A Harris Interactive poll conducted in Jan 2008 found that 944 of 1748 adult Amr

Question

A Harris Interactive poll conducted in Jan 2008 found that 944 of 1748 adult Amreicans 18 years or older who do not have a tattoo believe that individuals with tattoos are more rebellious. A 95% confidence interval for this result was calculated to be (0.517, 0.563). Under what conditions would the width of this confidence interval decrease?

Check all that apply.

If we sampled 1850 adults

If we wanted to use 90% confidence

If we sampled 1400 adults

If we wanted to use 99% confidence

If we sampled 1850 adults

If we wanted to use 90% confidence

If we sampled 1400 adults

If we wanted to use 99% confidence

Explanation / Answer

a) TRUE. If we increase the sample size, the width of confidence interval decreases. This is because it will decrease the standard error.

b) TRUE. If we dcrease the confidence level, the confidence interval decreases.

c) FALSE. If we decrease the sample size, the width of confidence interval increases. This is because it will increase the standard error.

d) FALSE.If we increase the confidence level, the confidence interval increases.

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