In a survey, 23 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $43 and standard deviation of $2. The best point estimate for μ is? The margin of error for a 95% confidence interval is?

In a random sample of 60 refrigerators, the mean repair cost was $157.08.  Assume the population standard deviation is $14.88 What is the LOWER endpoint of a 99% confidence interval for the population mean? What is the UPPER endpoint of a 99% confidence interval for the population mean?

The annual earnings of 13   randomly selected computer software engineers have a sample standard deviation of $ 3648 . Assume the sample is from a normally distributed population. Construct a confidence interval for the population variance sigma squared   and the population standard deviation sigma . Use a 95 %   level of confidence. Interpret the results. What is the confidence interval for the population variance sigma squared ​? What is the confidence interval for the population standard deviation sigma ​?

In a survey, 13 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $50 and standard deviation of $9. Find the margin of error at a 90% confidence level.