Which of the following will make a confidence interval narrower and more precise?

a. smaller sample size and higher confidence level
b. larger sample size and lower confidence level
c. smaller sample size and lower confidence level
d. larger sample size and higher confidence level

The confidence interval is the interval estimate of an unknown value of an information.

Reasons:

The confidence interval is given by the formula;

Where;

CI = The confidence interval

= The mean of the sample

z = The given confidence level

s = The sample standard deviation

n = The sample size

Therefore;

Similarly, we have;

The correct option is therefore, B. Larger sample size and lower confidence level.

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B. Larger sample size and lower confidence level

Step-by-step explanation:

The margin of error of a confidence interval is given by the following formula:

In which is the standard deviation of the population and n is the size of the sample.

z is related to the confidence level. The higher the confidence level, the higher the value of Z.

So, the margin of error is direct proportion to the confidence level and inverse proportional to the sample size.

We want to decrease the margin of error.

So the correct answer is:

B. Larger sample size and lower confidence level

answer: a. 74

step-by-step explanation:

it shows divided evenly, so add the 37+37 = 74