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ASTTBC Tech Exam study materials
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ASTTBC Tech Exam practice questions

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Question 1Applied Science Technology Practice

Which SI base unit is used to express the amount of a substance in chemical calculations?

  1. The mole Correct answer.
  2. The newton
  3. The candela
  4. The kelvin

Explanation

The mole is the SI base unit for amount of substance and is defined by a fixed number of elementary entities (the Avogadro constant). Chemical stoichiometry relies on counting particles in moles rather than in individual atoms or molecules.

Question 2Applied Science Technology Practice

A measured length is reported as 24.60 mm. How many significant figures does this value contain?

  1. Five
  2. Four Correct answer.
  3. Two
  4. Three

Explanation

Every non-zero digit is significant, and a trailing zero after a decimal point is also significant because it indicates the precision of the measurement. The digits 2, 4, 6 and the final 0 all count, giving four significant figures.

Question 3Applied Science Technology Practice

A technician converts a pressure reading of 250 kPa into pascals. Which value is correct?

  1. 250 000 Pa Correct answer.
  2. 25 000 Pa
  3. 2 500 000 Pa
  4. 2.5 Pa

Explanation

The prefix kilo means one thousand, so a value in kilopascals is multiplied by 1000 to obtain pascals. Multiplying 250 by 1000 gives 250 000 Pa.

Question 4Applied Science Technology Practice

In a technical report, which section normally states the purpose, scope and limitations of the work?

  1. The appendix
  2. The reference list
  3. The abstract
  4. The introduction Correct answer.

Explanation

The introduction establishes context for the reader by defining why the work was done, what it covers and what it deliberately excludes. Scope and limitation statements belong there so readers can judge how far the conclusions apply.

Question 5Applied Science Technology Practice

Which document type is most appropriate for specifying the step-by-step operation of a laboratory instrument so that different operators obtain consistent results?

  1. A material safety data sheet
  2. A non-conformance report
  3. A purchase requisition
  4. A standard operating procedure Correct answer.

Explanation

A standard operating procedure records the approved, repeatable sequence of steps for a task so that results are consistent regardless of who performs them. It is a controlled document subject to review and revision.

Question 6Applied Science Technology Practice

A data set of replicate measurements contains one value far outside the range of the others. What is the most defensible first step before deciding whether to discard it?

  1. Round all values to fewer significant figures
  2. Replace the value with the average of the remaining readings
  3. Delete the value immediately to protect the mean
  4. Investigate whether a recording or procedural error caused the value Correct answer.

Explanation

An outlier should be traced to its cause before any statistical treatment, because a documented error justifies exclusion whereas an unexplained value may be a genuine result. Investigation preserves the integrity of the data set and its conclusions.

Question 7Applied Science Technology Practice

Which statistical quantity is defined as the middle value of a data set arranged in order of magnitude?

  1. The median Correct answer.
  2. The range
  3. The mean
  4. The mode

Explanation

The median is the central observation once values are ranked, so half the data lie above it and half below. It is resistant to extreme values, which makes it useful for skewed measurements.

Question 8Applied Science Technology Practice

A worker must handle a corrosive solvent. Which control measure ranks highest in the hierarchy of hazard control?

  1. Eliminating the need for the solvent by changing the process Correct answer.
  2. Posting warning signs at the bench
  3. Providing training on safe handling
  4. Issuing personal protective equipment to the worker

Explanation

The hierarchy of controls places elimination and substitution above engineering, administrative and personal protective measures because removing the hazard protects everyone without relying on individual behaviour. Personal protective equipment is the last line of defence.

Question 9Applied Science Technology Practice

A rectangular sample measures 4.0 cm by 5.0 cm. What is its area expressed to the correct number of significant figures?

  1. 20.0 cm²
  2. 21 cm²
  3. 2.0 × 10¹ cm²
  4. 20 cm² Correct answer.

Explanation

Each factor has two significant figures, so the product must be reported with two significant figures. The calculated value 20 cm² therefore carries the correct precision, and writing extra zeros would overstate it.

Question 10Applied Science Technology Practice

A solution contains 12.5 g of solute dissolved in enough water to make 250 mL of solution. What is its concentration in grams per litre?

  1. 500 g/L
  2. 0.05 g/L
  3. 50 g/L Correct answer.
  4. 5 g/L

Explanation

Concentration in g/L equals mass in grams divided by volume in litres. Since 250 mL is 0.250 L, dividing 12.5 g by 0.250 L gives 50 g/L.

Question 11Applied Science Technology Practice

A technician needs 0.500 L of a 0.200 mol/L sodium chloride solution. What mass of sodium chloride is required? Use a molar mass of 58.4 g/mol.

  1. 29.2 g
  2. 5.84 g Correct answer.
  3. 2.92 g
  4. 11.7 g

Explanation

The amount of solute equals concentration multiplied by volume, giving 0.200 mol/L × 0.500 L = 0.100 mol. Multiplying by the molar mass of 58.4 g/mol gives 5.84 g.

Question 12Applied Science Technology Practice

A calibration certificate states an expanded uncertainty of ±0.2 mm at approximately 95 % confidence. How should a single measurement of 50.0 mm be reported?

  1. 50.0 ± 0.4 mm
  2. 50.0 ± 0.2 mm Correct answer.
  3. 50.0 ± 0.1 mm
  4. 50.0 mm

Explanation

The reported uncertainty should correspond to the stated confidence level, so the expanded uncertainty of 0.2 mm is quoted directly with the result. Halving or doubling it would misrepresent the confidence level attached to the interval.

Question 13Applied Science Technology Practice

Repeated measurements of a dimension give a mean of 10.02 mm with a standard deviation of 0.06 mm. What does the standard deviation describe?

  1. The probability that the mean is correct
  2. The true value of the dimension
  3. The spread of the individual readings about the mean Correct answer.
  4. The systematic offset of the instrument

Explanation

The standard deviation quantifies random scatter, expressing how widely individual observations are distributed around the mean. It does not identify bias, which is a systematic effect, nor does it establish the true value.

Question 14Applied Science Technology Practice

A result is calculated as 47.3 divided by 2.1. Using significant-figure rules, how should the answer be reported?

  1. 22.5
  2. 20
  3. 23 Correct answer.
  4. 22.52

Explanation

Division follows the least precise input, and 2.1 has only two significant figures. The unrounded quotient 22.52 is therefore reported as 23 with two significant figures.

Question 15Applied Science Technology Practice

A thermometer reads 0.4 °C high across its whole range. What type of error does this represent and how is it best addressed?

  1. Gross error, addressed by discarding all data
  2. Parallax error, addressed by changing the observer
  3. Systematic error, addressed by applying a correction Correct answer.
  4. Random error, addressed by taking more readings

Explanation

A consistent offset in one direction is a systematic error, also called bias, because it shifts every reading by the same amount. Replicate readings will not remove it, but a calibration correction derived from a reference standard will.

Question 16Applied Science Technology Practice

Which practice best supports traceability of a measurement result?

  1. Recording the result to as many decimal places as the display allows
  2. Calibrating the instrument against a reference standard linked to a national standard Correct answer.
  3. Averaging results from several different instruments
  4. Repeating each measurement at least ten times

Explanation

Traceability requires an unbroken chain of calibrations, each with stated uncertainty, linking the instrument to a recognised reference such as a national metrology standard. Documentation of that chain allows the result to be compared meaningfully with other measurements.

Question 17Applied Science Technology Practice

A technician records raw data in a bound laboratory notebook. Which practice best preserves the evidential value of that record?

  1. Erasing mistakes so the page stays legible
  2. Recording entries in pencil for easy correction
  3. Making corrections with a single line, initials and date while keeping the original visible Correct answer.
  4. Rewriting the notebook neatly at the end of each week

Explanation

Contemporaneous, indelible records with transparent corrections allow an independent reviewer to reconstruct what was actually observed and when. Single-line strike-throughs preserve the original entry so that the audit trail remains intact.

Question 18Applied Science Technology Practice

In a cause-and-effect diagram, which category of causes is conventionally examined alongside method, machine, material, measurement and environment?

  1. Profit
  2. Manpower or people Correct answer.
  3. Marketing
  4. Patents

Explanation

The classic cause-and-effect framework groups potential causes under people, method, machine, material, measurement and environment. People are included because human actions such as training and procedure adherence influence outcomes.

Question 19Applied Science Technology Practice

A process produces parts with a mean diameter equal to the target but with excessive spread. What does this indicate about the process capability?

  1. The process is centred but not capable of meeting the specification limits Correct answer.
  2. The process has no variation and is fully capable
  3. The specification limits are too wide for the process
  4. The process is off-centre and needs its mean adjusted

Explanation

Capability requires both a centred mean and sufficiently small variation relative to the tolerance. When the mean matches the target but the spread is large, parts fall outside the limits despite good centring, so the variation must be reduced.

Question 20Applied Science Technology Practice

A technician must present measurement results that are highly skewed by a few very large values. Which pair of summary statistics best conveys the typical value and the spread?

  1. Mean and standard deviation
  2. Mode and range
  3. Mean and range
  4. Median and interquartile range Correct answer.

Explanation

For skewed data the median and interquartile range are robust because they depend on position rather than on the magnitude of extreme values. Mean and standard deviation are both pulled strongly by outliers and can mislead.

Question 21Applied Science Technology Practice

A technician calculates a required reagent mass and obtains 4.876 g, but the balance available reads to 0.01 g. What is the appropriate action?

  1. Weigh 4.88 g and record it as the calculated value
  2. Weigh 4.88 g and record the actual balance reading Correct answer.
  3. Weigh 4.876 g by estimating between the smallest divisions
  4. Weigh 4.9 g to keep the record simple

Explanation

The recorded mass should reflect what the instrument can actually measure, and the actual reading, not the target, is what enters subsequent calculations. Estimating beyond the resolution of the balance creates a false impression of precision.

Question 22Applied Science Technology Practice

A sample is known to contain a component at a mass fraction near 0.05 %. Which analytical approach is most appropriate for quantifying it?

  1. A method whose detection limit equals 0.05 %
  2. A screening test that reports only presence or absence
  3. A trace-analysis technique with a detection limit well below 0.05 % Correct answer.
  4. A gravimetric method with a balance reading to 0.1 g

Explanation

Quantifying a minor component requires a method whose detection limit lies comfortably below the expected concentration, so that the measurement sits well above the noise floor. A detection limit equal to the analyte level gives unreliable quantification.

Question 23Applied Science Technology Practice

Two laboratories report the same mean for a certified reference material, but laboratory A's result lies within the certified uncertainty while laboratory B's does not. What is the most reasonable interpretation?

  1. Laboratory B's result proves the certified value is wrong
  2. Both laboratories are equally traceable because their means agree
  3. Laboratory B has greater random error but no bias
  4. Laboratory A shows no evidence of significant bias for this material Correct answer.

Explanation

Agreement within the stated uncertainty of a certified reference material provides evidence that a laboratory's result is free of detectable bias at that level. Disagreement beyond the uncertainty suggests a bias or an underestimated uncertainty in the other laboratory.

Question 24Applied Science Technology Practice

A measurement model combines two independent contributions with standard uncertainties of 3 units and 4 units. What is the combined standard uncertainty?

  1. 5 units Correct answer.
  2. 7 units
  3. 1 unit
  4. 12 units

Explanation

Independent uncertainty contributions combine in quadrature, so the combined standard uncertainty is the square root of the sum of the squares. The square root of 9 plus 16 is the square root of 25, which equals 5 units.

Question 25Applied Science Technology Practice

A technician must choose between two validated methods for the same analyte. Method 1 has a lower detection limit; Method 2 has a much smaller repeatability standard deviation at the concentration of interest. Which choice is best justified?

  1. Neither method, because validation removes all uncertainty
  2. Method 1, because a lower detection limit always improves results
  3. Method 2, because precision at the working concentration governs the reliability of reported values Correct answer.
  4. Either method, because both are validated

Explanation

At a concentration well above both detection limits, the decisive performance characteristic is the repeatability at that level, since it controls the confidence interval of the reported result. A lower detection limit matters mainly when measuring near trace levels.

Question 26Applied Science Technology Practice

A technician must report a measured length as 25.4 mm with an expanded uncertainty of ±0.3 mm. Which statement correctly expresses the confidence interval for the measurement?

  1. The true length is exactly 25.4 mm with no possible variation.
  2. The reported value should be rounded to 25 mm to match the uncertainty.
  3. The measurement error is guaranteed never to exceed 0.15 mm.
  4. The true length lies between 25.1 mm and 25.7 mm at the stated confidence level. Correct answer.

Explanation

An expanded uncertainty defines an interval around the measured value within which the true value is expected to lie at the stated confidence level. Adding and subtracting 0.3 mm from 25.4 mm gives 25.1 mm to 25.7 mm. The uncertainty describes a range, not a guarantee of exactness, and rounding to fewer digits is a separate reporting decision.

Question 27Applied Science Technology Practice

Which term describes the closeness of agreement between a measured value and the true or accepted reference value?

  1. Resolution
  2. Repeatability
  3. Trueness Correct answer.
  4. Precision

Explanation

Trueness is defined as the closeness of agreement between the average of an infinite number of replicate measured values and a reference value. Precision instead describes agreement among repeated measurements. Repeatability and resolution refer to consistency and smallest discernible change, not to closeness to a true value.

Question 28Applied Science Technology Practice

A technician needs to check that a volumetric pipette delivers its nominal volume accurately. Which procedure provides the most direct verification?

  1. Comparing the pipette visually against a beaker of similar size
  2. Reading the meniscus at eye level before each use
  3. Rinsing the pipette with the liquid to be dispensed
  4. Gravimetric delivery of distilled water at a known temperature, corrected for water density Correct answer.

Explanation

Gravimetric calibration converts the mass of water delivered into a volume using the known density at the measured temperature, giving a direct check of delivered volume. Meniscus reading, visual comparison, and rinsing are good operating practices but do not verify accuracy quantitatively.

Question 29Applied Science Technology Practice

Which document primarily specifies the general requirements for the competence of testing and calibration laboratories?

  1. ISO 14001
  2. ISO 9001
  3. ISO/IEC 17025 Correct answer.
  4. ISO 45001

Explanation

ISO/IEC 17025 sets out the general requirements for the competence, impartiality, and consistent operation of testing and calibration laboratories. ISO 9001 addresses quality management generally, while ISO 14001 and ISO 45001 cover environmental and occupational health and safety management.

Question 30Applied Science Technology Practice

A technician records a balance reading of 12.3456 g but the balance specification states a readability of 0.001 g. What is the most appropriate recorded value?

  1. 12.346 g Correct answer.
  2. 12.35 g
  3. 12.3 g
  4. 12.3456 g

Explanation

A recorded value should not imply more resolution than the instrument can provide. With readability of 0.001 g, the reading should be expressed to three decimal places, giving 12.346 g. Recording extra digits implies false precision, while coarser rounding discards usable resolution.

Question 31Applied Science Technology Practice

Which action best demonstrates ethical conduct when a technician discovers that a completed test was performed using an expired calibration standard?

  1. Waiting until the next scheduled audit to mention the issue
  2. Discarding the affected raw data so no one relies on it
  3. Recording the finding and reporting the affected results for review and possible retesting Correct answer.
  4. Quietly recalibrating the instrument and leaving the original records unchanged

Explanation

Professional ethics require honest, transparent disclosure of conditions that may invalidate results, followed by appropriate review. Documenting the issue and flagging affected results protects data integrity and allows corrective action. Recalibrating silently, destroying records, or delaying disclosure conceals a quality problem.

Question 32Applied Science Technology Practice

Which unit is the SI base unit of thermodynamic temperature?

  1. Degree Celsius
  2. Degree Fahrenheit
  3. Kelvin Correct answer.
  4. Joule

Explanation

The kelvin is the SI base unit of thermodynamic temperature. The degree Celsius is an accepted derived unit related to the kelvin by an offset, and the degree Fahrenheit is not part of the SI. The joule is the unit of energy.

Question 33Applied Science Technology Practice

A technician must dispose of a small quantity of waste solvent that is flammable and toxic. Which approach is most appropriate?

  1. Placing it in the general refuse bin
  2. Evaporating it in a fume hood to avoid liquid waste
  3. Collecting it in a compatible labelled container for hazardous waste disposal Correct answer.
  4. Pouring it down the sink with plenty of water

Explanation

Flammable and toxic solvents must be segregated into compatible, clearly labelled containers and consigned to a licensed hazardous waste stream. Drain disposal, general refuse, and deliberate evaporation all release hazardous substances into the environment or workplace air.

Question 34Applied Science Technology Practice

A control chart for a process shows all points within the control limits but exhibits a run of nine consecutive points on one side of the centre line. What does this pattern most likely indicate?

  1. A non-random shift in the process mean has occurred. Correct answer.
  2. The control limits were calculated incorrectly.
  3. The process is stable and no action is needed.
  4. The measurement resolution is too fine.

Explanation

A long run of consecutive points on one side of the centre line is a recognised non-random pattern indicating a sustained shift in the process mean. Even when individual points remain inside the limits, such runs signal special-cause variation requiring investigation. The pattern is not evidence of stability.

Question 35Applied Science Technology Practice

A technician measures a quantity five times and obtains 10.1, 10.3, 10.2, 10.2, and 10.2 units. What is the mean of these measurements?

  1. 10.1 units
  2. 10.25 units
  3. 10.2 units Correct answer.
  4. 10.3 units

Explanation

The mean is the sum of the values divided by the number of values. The sum is 51.0 units and dividing by five gives 10.2 units. Reporting 10.2 is consistent with the resolution of the recorded data.

Question 36Applied Science Technology Practice

A technician converts a pressure reading of 150 kPa into bar. Given that 1 bar equals 100 kPa, what is the reading in bar?

  1. 1500 bar
  2. 0.15 bar
  3. 1.5 bar Correct answer.
  4. 15 bar

Explanation

Dividing 150 kPa by 100 kPa per bar gives 1.5 bar. Unit conversion requires multiplying or dividing by the defined equivalence, so the numerical value decreases by a factor of one hundred. Checking the direction of the conversion guards against decimal errors.

Question 37Applied Science Technology Practice

A technician must select a sampling plan for a batch of material where the cost of failing to detect a defective item is very high. Which approach is most appropriate?

  1. A random sample drawn from throughout the batch with a tight acceptance criterion Correct answer.
  2. A single grab sample from the most accessible location
  3. A sample taken only after the batch has been shipped
  4. A small sample taken from the top of the container only

Explanation

When the consequences of missing a defect are high, the sampling plan should be representative and strict. Random sampling throughout the batch reduces bias, and a tight acceptance criterion lowers the risk of accepting nonconforming material. Convenience or top-only samples can miss segregation and variability.

Question 38Applied Science Technology Practice

A technician prepares a dilute acid solution and must add concentrated acid to water. Which practice is correct?

  1. Add the concentrated acid slowly to the water with stirring and cooling. Correct answer.
  2. Add the acid and water together and heat the mixture.
  3. Add water slowly to the concentrated acid while stirring.
  4. Mix the two rapidly in a sealed container.

Explanation

Diluting concentrated acid releases substantial heat, so the acid should be added slowly to water with stirring and cooling to control the temperature rise. Adding water to concentrated acid can cause local boiling and spattering. Sealed rapid mixing or external heating increases the risk of violent reaction.

Question 39Applied Science Technology Practice

A technician needs to determine whether the mean of a small set of measurements differs significantly from a certified value. Which statistical test is most appropriate when the population standard deviation is unknown?

  1. A chi-square goodness-of-fit test
  2. An F-test for variances
  3. A one-sample t-test Correct answer.
  4. A paired t-test

Explanation

A one-sample t-test compares a sample mean with a known or certified value when the population standard deviation is unknown and estimated from the sample. The chi-square test addresses categorical frequencies, the paired t-test compares paired differences, and the F-test compares variances.

Question 40Applied Science Technology Practice

A technician observes that a newly installed instrument gives readings that drift steadily upward during each working day. Which action is the most appropriate first step?

  1. Recalibrating the instrument once and assuming the drift has ended
  2. Applying a fixed correction factor to all readings
  3. Discarding all readings taken after midday
  4. Investigating possible causes such as warm-up, temperature, or power supply before adjusting results Correct answer.

Explanation

Systematic drift should be investigated at its source before any correction is applied, since the cause may be correctable through warm-up time, temperature control, or power stability. Applying arbitrary corrections or discarding data treats symptoms rather than the cause. A single recalibration may not address a continuing drift.

Question 41Applied Science Technology Practice

A technician must express a very large measured quantity, 4 500 000 m, in scientific notation with three significant figures. Which expression is correct?

  1. 4.5 × 10^6 m
  2. 45.0 × 10^5 m
  3. 4.50 × 10^6 m Correct answer.
  4. 4.500 × 10^6 m

Explanation

Scientific notation places one non-zero digit before the decimal point and uses a power of ten. Three significant figures require two digits after the decimal point, giving 4.50 × 10^6 m. The trailing zero must be shown to indicate the third significant figure.

Question 42Applied Science Technology Practice

A technician is asked to verify that a new analytical method gives results comparable to an established reference method on the same samples. Which approach is most appropriate?

  1. Checking that both methods use the same glassware
  2. Comparing the costs of the two methods
  3. Running the new method on a single sample and comparing with the manufacturer's claim
  4. Analysing the same samples by both methods and comparing paired results statistically Correct answer.

Explanation

Method comparison requires analysing the same samples by both procedures and evaluating the paired results for bias and agreement. A single sample or a literature claim does not establish comparability across the working range. Cost and glassware are unrelated to analytical agreement.

Question 43Applied Science Technology Practice

A technician calculates a 95 % confidence interval for a mean as 12.4 ± 0.6 units. Which interpretation is correct?

  1. If the sampling were repeated many times, about 95 % of such intervals would contain the true mean. Correct answer.
  2. The measurement uncertainty of each reading is 0.6 units.
  3. 95 % of individual measurements fall between 11.8 and 13.0 units.
  4. There is a 95 % chance that the true mean equals exactly 12.4 units.

Explanation

A confidence interval is a statement about the procedure: over repeated sampling, approximately 95 % of intervals constructed this way would contain the true mean. It does not describe the spread of individual measurements, nor does it assign a probability to the mean equalling a single value. The half-width is not the per-reading measurement uncertainty.

Question 44Applied Science Technology Practice

A technician must prepare a buffer solution at a specified pH and needs to confirm the result. Which check is most appropriate?

  1. Estimating the pH from the colour of the solution
  2. Measuring the volume of the solution with a graduated cylinder
  3. Measuring the pH with a meter calibrated against fresh standard buffers Correct answer.
  4. Assuming the calculated pH is correct without measurement

Explanation

A pH meter calibrated with fresh standard buffers bracketing the target range provides a direct and reliable check of the prepared pH. Colour is not a quantitative indicator for most buffers, calculation alone does not confirm preparation, and volume measurement does not verify pH.

Question 45Applied Science Technology Practice

A technician is asked to estimate the uncertainty of a calculated result that depends on three measured inputs. Which approach is most consistent with good metrological practice?

  1. Assigning a single arbitrary percentage to the final result
  2. Using only the largest input uncertainty and ignoring the others
  3. Combining the individual standard uncertainties according to how each input affects the result Correct answer.
  4. Reporting no uncertainty because the inputs were measured carefully

Explanation

An uncertainty budget propagates each input's standard uncertainty through the measurement model, weighted by its sensitivity to the result, and combines independent contributions. Arbitrary percentages or ignoring smaller contributions misrepresent the uncertainty. Careful measurement reduces but does not eliminate uncertainty.

Question 46Applied Science Technology Practice

A technician finds that a set of results has a mean close to the certified value but a standard deviation much larger than the method specification. Which conclusion is best supported?

  1. The method is unbiased but insufficiently precise for the intended use. Correct answer.
  2. The results are acceptable because the mean agrees with the certificate.
  3. The method is biased and must be recalibrated.
  4. The certified value is incorrect.

Explanation

Agreement of the mean with the certified value indicates little or no systematic bias, while an inflated standard deviation indicates poor precision. A method can be unbiased yet too variable for a purpose requiring tight results. Bias, certificate error, and acceptability of the mean alone are not supported by the evidence.

Question 47Applied Science Technology Practice

A technician must decide whether two sets of measurements taken by different operators have equal variances before choosing a comparison test. Which test is appropriate for this preliminary check?

  1. A sign test
  2. A one-sample t-test
  3. A chi-square test for independence
  4. An F-test Correct answer.

Explanation

The F-test compares the variances of two independent samples by forming the ratio of their variances. A one-sample t-test compares a mean with a value, the chi-square test for independence examines association between categorical variables, and the sign test assesses paired differences.

Question 48Applied Science Technology Practice

A technician is designing a measurement sequence to detect a small systematic difference between two instruments while minimising the influence of drift over time. Which design is best?

  1. Alternate or randomise the order of measurements between the two instruments Correct answer.
  2. Measure all samples with instrument A and compare with historical data
  3. Measure all samples with instrument A first, then all samples with instrument B
  4. Measure each sample only once with the instrument that seems more precise

Explanation

Alternating or randomising the order of measurements distributes any time-related drift across both instruments, preventing drift from being confounded with the instrument difference. Running one instrument entirely before the other allows drift to masquerade as a systematic difference. Single measurements and historical comparisons provide weaker control.

Question 49Applied Science Technology Practice

A technician must report a result whose combined standard uncertainty is 0.045 units and whose measured value is 12.318 units. Which reporting approach best follows good practice?

  1. Report 12 ± 0 units, rounding both to whole numbers
  2. Report 12.318 ± 0.045 units with no rounding
  3. Report 12.318 ± 0.0 units, omitting the uncertainty
  4. Report 12.32 ± 0.05 units, rounding the uncertainty to one significant figure and matching the value Correct answer.

Explanation

Good practice is to round the uncertainty to one or two significant figures and then round the measured value to the same decimal place. Here 0.045 rounds to 0.05, so the value becomes 12.32. Reporting unmatched digits or omitting the uncertainty misrepresents the measurement.

Question 50Applied Science Technology Practice

A technician needs to record a measured volume of 25.0 mL in a laboratory notebook that will serve as a legal record of the test. Which practice best meets good documentation requirements?

  1. Record the value in permanent ink with the date, the technician's initials, and the unit, and cross out any error with a single line that remains legible. Correct answer.
  2. Record the value in permanent ink and, if an error is found, overwrite the digits so the final figure is clearly readable.
  3. Record the value in pencil so that any later correction can be made cleanly without leaving a trace of the original entry.
  4. Record the value on a loose sheet of paper and transfer it to the official notebook at the end of the week.

Explanation

Good laboratory documentation requires entries that are permanent, attributable, and contemporaneous, so the record shows who recorded what and when. Errors must be corrected with a single line so the original entry stays legible, preserving an audit trail. Ink prevents undetected alteration, and including the unit avoids later ambiguity about the measurement.