A random sample of size n has been selected from a normally distributed populati

Question

A random sample of size n has been selected from a normally distributed population whose standard deviation is ?. In hypothesis testing for the population mean, the t-test should be used instead of the z-test if:

A. n>30 and ? is unknown

B. n<30 and ? is known

C. both A and B are true

D. both A and B are false

In selecting the sample size to estimate the population proportion p , if we have no knowledge of even the approximate value of the sample proportion p? , we:

A. let p? =0.50

B. let p? =0.95

C. take another sample and estimate p?

D. take two more samples and find the average of their p?

Explanation / Answer

1)

If sigma is unknown and the sample size is less than 30

We use t test instead of Z test.

2)

When we don't have the knowledge about the sample proportion is

p ^ = 0.50

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