Normal Probability Sample Means

What happens to the shape of a sampling distribution of sample means as n increases?

• It becomes narrower and bimodal.
• It becomes narrower and more normal.
• It becomes wider and skewed right. 
• It becomes wider and more normal. 

The mean and standard deviation of a population are 400 and 40, respectively. Sample size is 25. 
What is the mean of the sampling distribution?

• 400
• 40
• 25
• 8

The mean and standard deviation of a population are 400 and 40, respectively. Sample size is 25. 
What is the standard error of the sampling distribution?

• 400
• 40
• 25
• 8

A sample of 30 women finds the mean height to be 62.3 in The population standard deviation was found to be 1.5 in. Find the margin of error of women's heights with a 95% CL.

• 1.699

• 0.65

• 0.537

• 19.325

Which of the following does NOT have an affect on the width of a confidence interval?

• Sample mean

• z*

• Sample standard deviation

• Sample size

A 90% confidence interval for a population mean is determined to be 800 to 900. If the confidence is increased to 95% confidence while the sample statistics and sample size remain the same, the confidence interval

• becomes wider
• becomes narrower
• does not change

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting one data value less than 190?

• 69%
• 42%
• 31%
• 58%

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting 25 data values with a mean less than 190?

• 69%
• 0.6%
• 31%
• 99%

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting 64 data values with a mean between 195 and 200?

• 41%%
• 48%
• 1.5%
• 0.5%

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting 100 data values with a mean greater than 202?

• 45%
• 36%
• 25%
• 16%