"quantity"exercise:Confidence level
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Questions 1:
An increase in which of the following items will most likely result in a wider confidence interval for the population mean?
A、 Reliability factor
B 、Sample size
C 、Degrees of freedom
Questions 2:
The following ten observations are a sample drawn from an approximately normal population:
The sample standard deviation is closest to:
A 、17.56.
B、 19.59.
C、 18.58.
A is correct. An increase in the reliability factor (the degree of confidence) increases the width of the confidence interval. Increasing the sample size and increasing the degrees of freedom both shrink the confidence interval. B is incorrect. Increasing the sample size shrinks the confidence interval. C is incorrect. Increasing the degrees of freedom shrinks the confidence interval.
B is correct.
The sample standard deviation is the (positive) square root of the sample variance:
A is incorrect. 17.56 is the sum of the absolute value of the deviations from mean divided by 9:
C is incorrect and is calculated by dividing the sum of squared deviations by 10 rather than 9: 3,453.60/10 = 18.58.
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