Engineering Metrology Mcqs


Which option is not correct about coverage factor?

A) It is a number which is generally larger than 1 B) Range – 2 to 7
C) Can be calculated by using MS excel D) Depends on the selected coverage probability
Answer & Explanation Answer: B) Range – 2 to 7

Explanation: The coverage factor generally depends upon the probability distribution type of the output measurement quantity in the measurement model and on the selected coverage probability. Its range is generally between 2 to 3, can be more for special purposes.

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Which of the following option is true for given statements about expanded uncertainty and coverage factor?
Statement 1: Last calculation is the expanded uncertainty when estimating uncertainty in measurement.
Statement 2: In metrology industry, the mostly used value of the coverage factor is 2.

A) T, F B) F, F
C) T, T D) F, T
Answer & Explanation Answer: C) T, T

Explanation: In metrology industry, a typically estimate of uncertainty to 95.45% confidence and coverage factor where k=2 is used. It can vary according to requirement. Last calculation is generally the expanded uncertainty while estimating measurement uncertainty.

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What is the value of coverage factor which is generally used in the manufacturing industry?

A) 2 B) 2.89
C) 3 D) 3.89
Answer & Explanation Answer: D) 3.89

Explanation: In the manufacturing industry, the main aim is for a failure rate of 1 in ten thousand or a coverage factor ‘k’ of 99.99% confidence, where coverage factor = 3.89. However, Confidence intervals can be greater or smaller for different industries depending on acceptable failure rates.

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Which table is generally used to find the coverage factor?

A) Student’s T table B) F distribution table
C) Wishart distribution table D) Tau distribution table
Answer & Explanation Answer: A) Student’s T table

Explanation: Student’s T table is generally used to find coverage factor. The values are generally found at the bottom of the table especially the last row and it is generally marked with the infinity (?) symbol.

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What is the confidence interval for the value of coverage factor ‘2’?

A) 95 % B) 94 %
C) 95.45 % D) 94.45 %
Answer & Explanation Answer: C) 95.45 %

Explanation: Confidence interval for the value of coverage factor 2 is generally taken as 95 % but it is not the actual value. The actual value for this is 95.45 %. For 95 % confidence interval, actual ‘k’ or coverage factor is 1.96.

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Which distribution is related to U-probability distribution of Type-B evaluation of uncertainty?

A) Arcsin distribution B) Binomial distribution
C) Poisson distribution D) Bernoulli distribution
Answer & Explanation Answer: A) Arcsin distribution

Explanation: U-probability distribution of Type-B evaluation method of uncertainty is used when the values are at extreme limits and values are least at mean for example Arcsin distribution. Standard uncertainty = a/?2.

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Which of the following is not treated as Type-B uncertainty?

A) Hysteresis B) Common Mode Voltage
C) Nonlinearity D) Repeatability
Answer & Explanation Answer: D) Repeatability

Explanation: Resolution, Scale Size and Quantization, Hysteresis, Common Mode Voltage, Installation, Nonlinearity or Linearity, Spatial Variation, Loading uncertainties, Sensitivity and Zero offset, these all are Type-B uncertainties.

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What is the relation of expanded uncertainty with coverage factor and combined uncertainty?

A) Expanded uncertainty = Coverage factor * Combined uncertainty B) Combined uncertainty = Coverage factor * Expanded uncertainty
C) Coverage factor = Combined uncertainty * Expanded uncertainty D) Coverage factor * Combined uncertainty * Expanded uncertainty = 1
Answer & Explanation Answer: A) Expanded uncertainty = Coverage factor * Combined uncertainty

Explanation: The equation which is used to calculate expanded uncertainty is a very basic equation. To calculate expanded uncertainty, one will need to multiply a coverage factor by the combined uncertainty.

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