Confidence Intervals for a Single Mean

A sample of 100 observations is collected and yields m=75 and s=8. Find a 95% confidence interval for the true population average.

For a sample of 121 observations with an average of 50 and standard deviation of 20, find a 90% confidence interval for the true population average.

Kennesaw State University claims the average starting salary of its graduates is $38,500. A sample of 100 KSU students is sampled and yields an average starting salary of $36,800 with a standard deviation of $9,369. Using a 95% confidence level what can you say about KSU's claim?

The larger the sample the smaller the margin of error is.  What happens with very small samples?

Find a 99% confidence interval for the true population average from which the sample S={229, 255, 280, 203, 229} is randomly selected.

Confidence Intervals for the Difference of Two Means

Two types of flares are tested for their burning times (in minutes) and sample results are given below.

 

Construct a 95% confidence interval to determine if there exists a difference of average burning times based on the sample data.

A researcher wishes to determine whether people with high blood pressure can reduce their blood pressure by following a particular diet. Use the sample data below to construct a 99% confidence interval for
m1 - m2 where m1 and m2 represent the mean for the treatment group and the control group respectively.  Explain your results.