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RRB Lab Technician study materials
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RRB Lab Technician practice questions

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Question 1Mathematics

A laboratory reports a blood glucose result as 5.6 mmol/L. What is this value in mg/dL, using the conversion factor 18 mg/dL per mmol/L?

  1. 180.0 mg/dL
  2. 31.1 mg/dL
  3. 56.0 mg/dL
  4. 100.8 mg/dL Correct answer.

Explanation

To convert mmol/L to mg/dL for glucose, multiply by 18. So 5.6 × 18 = 100.8 mg/dL. This factor reflects the molar mass of glucose and is standard in clinical chemistry reporting.

Question 2Mathematics

A technician must prepare 250 mL of a 0.9% (w/v) sodium chloride solution. What mass of NaCl is required?

  1. 0.9 g
  2. 22.5 g
  3. 2.25 g Correct answer.
  4. 9.0 g

Explanation

Percent w/v means grams of solute per 100 mL of solution. A 0.9% solution contains 0.9 g per 100 mL, so 250 mL requires 0.9 × 2.5 = 2.25 g.

Question 3Mathematics

A urine specimen is diluted 1:10 and the diluted sample reads 40 mg/dL on the analyzer. What is the concentration in the original specimen?

  1. 40 mg/dL
  2. 400 mg/dL Correct answer.
  3. 4 mg/dL
  4. 0.4 mg/dL

Explanation

A 1:10 dilution means the specimen was diluted tenfold, so the measured value must be multiplied by the dilution factor. 40 × 10 = 400 mg/dL in the original sample.

Question 4Mathematics

Which of the following is the SI base unit for the amount of substance, used when expressing concentrations in clinical chemistry?

  1. The mole Correct answer.
  2. The litre
  3. The gram
  4. The newton

Explanation

The mole is the SI base unit for amount of substance and underlies molar concentration units such as mmol/L. Grams measure mass, litres measure volume, and newtons measure force.

Question 5Mathematics

A technician calculates a mean of 50.0 for five replicate measurements: 48, 52, 50, 49, and 51. What is the mean?

  1. 51.0
  2. 50.0 Correct answer.
  3. 49.0
  4. 52.5

Explanation

The mean is the sum of the values divided by the number of values: (48 + 52 + 50 + 49 + 51) = 250, and 250 ÷ 5 = 50.0. The mean is the arithmetic average of the replicates.

Question 6Mathematics

A calibrated pipette is stated to deliver 100 µL. Expressed in millilitres, this volume is:

  1. 0.010 mL
  2. 10.0 mL
  3. 0.100 mL Correct answer.
  4. 1.000 mL

Explanation

There are 1000 µL in 1 mL, so 100 µL ÷ 1000 = 0.100 mL. Microlitre volumes are common when dispensing small sample aliquots.

Question 7Mathematics

A quality-control chart shows a single control result exactly at +2 standard deviations. Which statement correctly describes this result?

  1. It exceeds the upper control limit
  2. It indicates a random error that must be rejected
  3. It proves a systematic shift in the assay
  4. It lies within the acceptable ±2 SD control limits Correct answer.

Explanation

Control limits are conventionally set at the mean ±2 SD, so a value exactly at +2 SD is at the boundary but still within acceptable limits. Values beyond 2 SD, or trends across runs, are what trigger investigation.

Question 8Mathematics

A specimen is reported as having a glucose concentration of 90 mg/dL. If the molecular mass of glucose is 180 g/mol, what is the molar concentration?

  1. 0.5 mmol/L
  2. 500 mmol/L
  3. 5.0 mmol/L Correct answer.
  4. 50 mmol/L

Explanation

90 mg/dL = 900 mg/L. Dividing by 180 g/mol (900 ÷ 180) gives 5.0 mmol/L. This is equivalent to dividing mg/dL by 18 for glucose.

Question 9Mathematics

A technician needs 500 mL of a 2 mol/L solution from a 10 mol/L stock. What volume of stock is required?

  1. 50 mL
  2. 250 mL
  3. 200 mL
  4. 100 mL Correct answer.

Explanation

Use C1V1 = C2V2: 10 × V1 = 2 × 500, so V1 = 1000 ÷ 10 = 100 mL. The stock is diluted to 500 mL final volume.

Question 10Mathematics

The following counts of white blood cells were recorded in five fields: 8, 10, 12, 14, and 16. What is the standard deviation of this sample?

  1. 12.0
  2. 10.0
  3. 2.83
  4. 3.16 Correct answer.

Explanation

The mean is 12. Squared deviations sum to 16 + 4 + 0 + 4 + 16 = 40. Dividing by n−1 = 4 gives 10, and √10 ≈ 3.16. Using n rather than n−1 gives 2.83, which is the population value.

Question 11Mathematics

A result of 8.0 g/dL is reported when the true value is 8.4 g/dL. What is the percentage error?

  1. Approximately 0.48%
  2. Approximately 5.0%
  3. Approximately 0.4%
  4. Approximately 4.8% Correct answer.

Explanation

Percentage error = (true − measured) ÷ true × 100 = (0.4 ÷ 8.4) × 100 ≈ 4.8%. The error is expressed relative to the true value, not the measured value.

Question 12Mathematics

A technician must prepare 1 L of a 0.15 mol/L NaCl solution. The molar mass of NaCl is 58.5 g/mol. How much NaCl is needed?

  1. 58.5 g
  2. 8.78 g Correct answer.
  3. 1.50 g
  4. 5.85 g

Explanation

Mass = concentration × volume × molar mass = 0.15 × 1 × 58.5 = 8.775 g, which rounds to 8.78 g. This uses the definition of molarity as moles per litre.

Question 13Mathematics

A dilution series is set up as 1:2, then 1:2, then 1:2. What is the total dilution factor of the final tube?

  1. 1:8 Correct answer.
  2. 1:6
  3. 1:2
  4. 1:4

Explanation

Serial dilution factors multiply: 2 × 2 × 2 = 8, so the final tube is a 1:8 dilution. Each step halves the concentration again.

Question 14Mathematics

In a set of results, the median differs markedly from the mean because of one extreme outlier. Which measure of central tendency is most affected by that outlier?

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

Explanation

The mean uses every value in its calculation, so a single extreme outlier pulls it strongly. The median and mode depend on position or frequency and are more resistant to outliers.

Question 15Mathematics

A laboratory measures a sample six times and obtains values with a mean of 100 mg/dL and a standard deviation of 2 mg/dL. Which statement best interprets the coefficient of variation?

  1. The CV is 50%, indicating poor precision
  2. The CV is 2%, indicating relatively good precision Correct answer.
  3. The CV is 20%, indicating acceptable precision
  4. The CV is 0.02%, indicating excellent precision

Explanation

The coefficient of variation is the standard deviation divided by the mean, expressed as a percentage: (2 ÷ 100) × 100 = 2%. A CV of 2% indicates relatively good precision for this assay.

Question 16Mathematics

A technician measures a 25 mL sample with a graduated cylinder. The volume is recorded as 25.0 mL. How many significant figures does this measurement have?

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

Explanation

The digits 2, 5, and the trailing zero after the decimal point are all significant, giving three significant figures. The trailing zero is significant because it follows a decimal point.

Question 17Mathematics

A spectrophotometer reads an absorbance of 0.30 for a sample. If the molar absorptivity is 150 L/(mol·cm) and the path length is 1 cm, what is the concentration?

  1. 0.200 mol/L
  2. 0.020 mol/L
  3. 2.0 mol/L
  4. 0.002 mol/L Correct answer.

Explanation

Beer-Lambert law: A = εbc, so c = A ÷ (εb) = 0.30 ÷ (150 × 1) = 0.002 mol/L. The concentration is directly proportional to absorbance.

Question 18Mathematics

A technician performs a two-fold serial dilution starting from 200 mg/dL and makes four successive 1:2 dilutions. What is the concentration in the fourth tube?

  1. 50 mg/dL
  2. 12.5 mg/dL Correct answer.
  3. 6.25 mg/dL
  4. 25 mg/dL

Explanation

Four successive 1:2 dilutions give a total factor of 2⁴ = 16. Dividing 200 by 16 gives 12.5 mg/dL in the fourth tube.

Question 19Mathematics

A control result falls beyond the mean +3 SD on a Levey-Jennings chart. Which action is most appropriate?

  1. Report the results because a single point beyond 3 SD is expected occasionally
  2. Reject the run and investigate the cause before reporting patient results Correct answer.
  3. Repeat the control once and report if it falls within 2 SD
  4. Recalibrate the instrument and report the original results

Explanation

A single control value beyond ±3 SD is a standard rejection rule indicating an out-of-control run. Patient results should be withheld until the cause is identified and corrected.

Question 20Mathematics

A sample of 10 measurements has a mean of 40 and a standard deviation of 4. What is the standard error of the mean?

  1. Approximately 1.26 Correct answer.
  2. Approximately 0.40
  3. Approximately 12.6
  4. Approximately 4.0

Explanation

The standard error of the mean equals the standard deviation divided by the square root of n: 4 ÷ √10 ≈ 4 ÷ 3.16 ≈ 1.26. It quantifies the precision of the estimated mean.

Question 21Mathematics

A technician needs 50 mL of a 5% (v/v) ethanol solution from a 95% (v/v) stock. Which calculation gives the required stock volume?

  1. (95 × 50) ÷ 5 = 950 mL
  2. (5 ÷ 95) × 50 ≈ 2.63 mL
  3. (5 × 50) ÷ 95 ≈ 2.63 mL Correct answer.
  4. (50 ÷ 5) × 95 = 950 mL

Explanation

Applying C1V1 = C2V2 gives 95 × V1 = 5 × 50, so V1 = 250 ÷ 95 ≈ 2.63 mL. The stock is then made up to 50 mL with diluent.

Question 22Mathematics

A laboratory reports a serum creatinine of 1.2 mg/dL. Given that 1 mg/dL of creatinine corresponds to approximately 88.4 µmol/L, what is the value in µmol/L?

  1. Approximately 74 µmol/L
  2. Approximately 1 060 µmol/L
  3. Approximately 106 µmol/L Correct answer.
  4. Approximately 10.6 µmol/L

Explanation

Multiply the mg/dL value by 88.4: 1.2 × 88.4 ≈ 106 µmol/L. This factor reflects the molar mass of creatinine and is standard for unit conversion.

Question 23Mathematics

Two technicians each measure the same sample five times. Technician A obtains a mean of 100 with SD 1; Technician B obtains a mean of 100 with SD 5. Which conclusion is best supported?

  1. B is more accurate because its spread is larger
  2. Both are precise, but A is more accurate
  3. Both are accurate, but A is more precise Correct answer.
  4. A is both more accurate and more precise

Explanation

Accuracy refers to closeness to the true value, while precision refers to agreement among replicate measurements. Both means equal 100, so accuracy is similar, but the smaller SD for A indicates better precision.

Question 24Mathematics

A laboratory's control data show seven consecutive results all on one side of the mean. Which rule does this violate, and what does it suggest?

  1. The R-4S rule, suggesting random error
  2. The 1-3S rule, suggesting random error
  3. No rule is violated if all values remain within 2 SD
  4. A trend/shift rule, suggesting systematic error Correct answer.

Explanation

Seven or more consecutive points on one side of the mean indicate a shift or trend, which typically signals systematic error such as calibration drift or reagent deterioration. Random error would scatter on both sides of the mean.

Question 25Mathematics

A technician dilutes a 12 g/dL hemoglobin sample by mixing 0.5 mL of sample with 4.5 mL of diluent. The diluted sample reads 1.2 g/dL. What is the dilution factor and the calculated original value?

  1. Factor 5; original value 6 g/dL
  2. Factor 10; original value 12 g/dL Correct answer.
  3. Factor 10; original value 1.2 g/dL
  4. Factor 9; original value 10.8 g/dL

Explanation

The total volume is 0.5 + 4.5 = 5.0 mL, so the sample was diluted 5.0 ÷ 0.5 = 10-fold. Multiplying the diluted reading by 10 gives 1.2 × 10 = 12 g/dL, matching the expected value.

Question 26Mathematics

A lab technician records a red blood cell count as 4.5 × 10^6 cells/µL. Expressed in standard scientific notation as cells/L, this is:

  1. 4.5 × 10^6 cells/L
  2. 4.5 × 10^3 cells/L
  3. 4.5 × 10^12 cells/L Correct answer.
  4. 4.5 × 10^9 cells/L

Explanation

One litre contains 10^6 microlitres, so a count per µL must be multiplied by 10^6 to convert to per litre. Thus 4.5 × 10^6 cells/µL becomes 4.5 × 10^6 × 10^6 = 4.5 × 10^12 cells/L. This unit conversion is routine when reporting haematology counts in SI units.

Question 27Mathematics

A laboratory reports a serum potassium result of 5.0 mmol/L. Converted to mEq/L, the value is:

  1. 10.0 mEq/L
  2. 5.0 mEq/L Correct answer.
  3. 2.5 mEq/L
  4. 0.5 mEq/L

Explanation

For a monovalent ion such as potassium, one millimole carries one milliequivalent, so the numerical value in mmol/L equals that in mEq/L. Therefore 5.0 mmol/L is 5.0 mEq/L. Only for ions of higher valence does the equivalence factor differ.

Question 28Mathematics

A technician prepares a 1:5 dilution of a serum sample and the diluted result reads 30 mg/dL. What is the concentration in the original undiluted sample?

  1. 35 mg/dL
  2. 120 mg/dL
  3. 6 mg/dL
  4. 150 mg/dL Correct answer.

Explanation

A 1:5 dilution means the sample was diluted five-fold, so the measured value must be multiplied by the dilution factor to recover the original concentration. Here 30 mg/dL × 5 = 150 mg/dL. The dilution factor is the reciprocal of the fraction of sample present.

Question 29Mathematics

A technologist mixes 2 mL of serum with 8 mL of saline. The resulting dilution expressed as a ratio (sample to total volume) is:

  1. 1:4
  2. 1:5 Correct answer.
  3. 2:8
  4. 1:10

Explanation

The total volume is 2 mL sample plus 8 mL diluent, which equals 10 mL. The ratio of sample to total volume is therefore 2:10, which simplifies to 1:5. Expressing the dilution against total volume, not against diluent alone, avoids the common 1:4 error.

Question 30Mathematics

A laboratory's daily glucose control has a mean of 100 mg/dL and a standard deviation of 4 mg/dL. A single control result of 91 mg/dL is plotted. Using the standard deviation index, how many standard deviations from the mean is this result, and does it fall outside the ±2 SD acceptable limit?

  1. 2.25 SD from the mean; it is within the ±2 SD limit
  2. 2.25 SD from the mean; it is outside the ±2 SD limit Correct answer.
  3. 1.25 SD from the mean; it is within the ±2 SD limit
  4. 9 SD from the mean; it is outside the ±2 SD limit

Explanation

The standard deviation index equals (result − mean) ÷ SD, which here is (91 − 100) ÷ 4 = −2.25. The magnitude, 2.25 SD, exceeds the ±2 SD acceptance limit, so the result is out of control and should trigger investigation. The sign is negative because the value lies below the mean.

Question 31General Intelligence and Reasoning

A lab technician notes that a reagent bottle expires 45 days after opening. If it was opened on 3 March, on which date does it expire?

  1. 17 April Correct answer.
  2. 18 April
  3. 15 April
  4. 16 April

Explanation

March has 31 days, so 28 days remain in March after the 3rd. Subtracting 28 from 45 leaves 17 days into April, giving 17 April as the expiry date.

Question 32General Intelligence and Reasoning

In a lab register the code for a specimen is written as SPECIMEN. If every letter is shifted one place forward in the alphabet, what does the code become?

  1. TQFDJNFM
  2. TQFEJNFN
  3. TQFDJNFN Correct answer.
  4. RQFDJNFN

Explanation

A forward shift of one converts S to T, P to Q, E to F, C to D, I to J, M to N, E to F, N to O, giving TQFDJNFN. Each letter must move exactly one position, so the pattern is verified letter by letter.

Question 33General Intelligence and Reasoning

A technician's report lists sample numbers 2, 6, 12, 20, 30. What is the next sample number in this series?

  1. 40
  2. 44
  3. 42 Correct answer.
  4. 38

Explanation

The differences between consecutive terms are 4, 6, 8 and 10, increasing by two each time. The next difference is 12, so 30 + 12 = 42.

Question 34General Intelligence and Reasoning

In a lab, Ravi is taller than Suman but shorter than Tara. Tara is shorter than Uma. Who is the tallest among the four?

  1. Uma Correct answer.
  2. Tara
  3. Ravi
  4. Suman

Explanation

The chain runs Suman < Ravi < Tara < Uma, since Tara is shorter than Uma. Uma stands at the top of this ordering and is therefore the tallest.

Question 35General Intelligence and Reasoning

A lab assistant's workstation faces north. She turns 90 degrees clockwise, then 180 degrees, then 90 degrees anticlockwise. Which direction is she facing now?

  1. North
  2. West
  3. South Correct answer.
  4. East

Explanation

Starting north, a 90-degree clockwise turn faces east; 180 degrees more faces west; then 90 degrees anticlockwise from west faces south. Net rotation is 180 degrees clockwise, which from north gives south.

Question 36General Intelligence and Reasoning

Which word among the following is most closely related to the working of a centrifuge in a laboratory?

  1. Separation Correct answer.
  2. Calibration
  3. Staining
  4. Incubation

Explanation

A centrifuge spins samples so that components of different density separate into layers. The other terms describe staining of slides, controlled warming of cultures, and adjustment of instruments, none of which is the centrifuge's purpose.

Question 37General Intelligence and Reasoning

If LAB is coded as 12-1-2 using alphabet positions, how is TEST coded in the same scheme?

  1. 20-4-19-20
  2. 20-5-19-20 Correct answer.
  3. 19-5-19-20
  4. 20-5-18-20

Explanation

Alphabet positions give T=20, E=5, S=19 and T=20, so TEST becomes 20-5-19-20. Each letter is replaced by its standard position number in the alphabet.

Question 38General Intelligence and Reasoning

A reagent shelf holds bottles in the order A, B, C, D, E. If the middle bottle is removed and the rest keep their order, which bottle is now in the middle position?

  1. B
  2. C
  3. E
  4. D Correct answer.

Explanation

The middle bottle of five is C, the third one. Removing C leaves A, B, D, E, whose middle two positions are B and D; the third position is now D.

Question 39General Intelligence and Reasoning

A lab has 3 racks, each holding 4 trays, and each tray holds 5 test tubes. How many test tubes can be stored in total?

  1. 50
  2. 60 Correct answer.
  3. 55
  4. 45

Explanation

Multiply the levels: 3 racks times 4 trays gives 12 trays, and 12 trays times 5 tubes gives 60 test tubes. The calculation is a straightforward product of the three counts.

Question 40General Intelligence and Reasoning

Five specimens are stored in racks numbered 1 to 5 from left to right. The blood sample is in rack 4, the urine sample is immediately left of the blood sample, and the swab is in rack 1. Which rack holds the urine sample?

  1. Rack 5
  2. Rack 2
  3. Rack 3 Correct answer.
  4. Rack 4

Explanation

The urine sample is immediately left of the blood sample in rack 4, so it must be in rack 3. The swab in rack 1 is consistent with this and does not affect the urine position.

Question 41General Intelligence and Reasoning

In a certain code, REAGENT is written as TFCI GPV. If the same rule applies, how is SAMPLE written?

  1. UCNNRF
  2. UCNNRG Correct answer.
  3. TCNNRG
  4. UCOORG

Explanation

Each letter of REAGENT is shifted two places forward: R to T, E to G, A to C, and so on. Applying the same +2 shift to SAMPLE gives U, C, N, N, R, G, that is UCNNRG.

Question 42General Intelligence and Reasoning

A technician's log records: 'All centrifuges in Lab A are calibrated. Some calibrated instruments in Lab A are new.' Which conclusion follows necessarily?

  1. Some centrifuges are new
  2. Some instruments in Lab A are calibrated Correct answer.
  3. All calibrated instruments are centrifuges
  4. All new instruments are centrifuges

Explanation

Since all centrifuges in Lab A are calibrated, and centrifuges exist there, at least some instruments in Lab A are calibrated. The statement about new instruments does not force any overlap with centrifuges.

Question 43General Intelligence and Reasoning

A bench clock shows 3:30. What is the angle between the hour hand and the minute hand?

  1. 85 degrees
  2. 75 degrees Correct answer.
  3. 80 degrees
  4. 90 degrees

Explanation

At 3:30 the minute hand points at 6 (180 degrees) and the hour hand has moved half past 3, sitting at 105 degrees. The difference is 75 degrees.

Question 44General Intelligence and Reasoning

Study the pattern: 3, 9, 27, 81, ? What is the next number?

  1. 324
  2. 162
  3. 216
  4. 243 Correct answer.

Explanation

Each term is multiplied by 3 to give the next: 3, 9, 27, 81, then 81 times 3 equals 243. The series is a simple geometric progression with ratio 3.

Question 45General Intelligence and Reasoning

In a row of test tubes, the red tube is 7th from the left and 5th from the right. How many test tubes are in the row?

  1. 13
  2. 12
  3. 11 Correct answer.
  4. 10

Explanation

When an item is nth from one end and mth from the other, the total is n + m - 1. Here 7 + 5 - 1 = 11 test tubes.

Question 46General Intelligence and Reasoning

A lab assistant walks 5 m north, turns right and walks 3 m, then turns right and walks 5 m. How far is she from the starting point?

  1. 8 m
  2. 5 m
  3. 13 m
  4. 3 m Correct answer.

Explanation

Walking 5 m north then 5 m south cancels the north-south displacement, leaving only the 3 m eastward leg. The straight-line distance back to the start is therefore 3 m.

Question 47General Intelligence and Reasoning

In a coded language, 'pipette is glass' is written 'ka la ma', 'glass is fragile' is written 'ma na pa', and 'fragile needs care' is written 'pa ra sa'. Which code stands for 'glass'?

  1. na
  2. ma Correct answer.
  3. ka
  4. la

Explanation

'Glass' appears in the first two sentences, whose only shared code word is 'ma'. Therefore 'ma' represents glass. Checking 'is' gives 'la' and 'fragile' gives 'pa', which is consistent.

Question 48General Intelligence and Reasoning

A technician's report has the statements: 'No unlabelled tube is stored in Rack B' and 'All tubes in Rack B are sterile.' Which conclusion is valid?

  1. All sterile tubes are in Rack B
  2. Some labelled tubes are sterile
  3. All unlabelled tubes are non-sterile
  4. No unlabelled tube in Rack B is non-sterile Correct answer.

Explanation

Since no unlabelled tube is in Rack B, any unlabelled tube in Rack B is vacuously sterile, so none there is non-sterile. The other options extend the premises beyond Rack B or reverse the direction of the relation.

Question 49General Intelligence and Reasoning

A reagent's concentration doubles every hour. If it starts at 2 units at 8 a.m., at what time does it first exceed 60 units?

  1. 11 a.m.
  2. 12 noon
  3. 2 p.m.
  4. 1 p.m. Correct answer.

Explanation

The values are 2, 4, 8, 16, 32 and 64 at successive hours from 8 a.m. The value 64 first exceeds 60 at 1 p.m., after five doublings.

Question 50General Intelligence and Reasoning

A lab schedule rotates duties: Ana works days 1, 4, 7, 10 and so on. On which of the following days will Ana also work?

  1. Day 27
  2. Day 25
  3. Day 22 Correct answer.
  4. Day 20

Explanation

Ana's working days follow the pattern 1, 4, 7, 10, which are numbers of the form 3k + 1. Day 22 equals 3 times 7 plus 1, so it fits the pattern.