population size = 70, sample size = 40, assume the sample follows normal distribution, sample mean = 57, sample standard deviation s = 19, pupulation standard σ is unknown.   a) Find the 90% confidence interval for the average customer score. b) For the given margin of error 4, what do you think would be the minimum sample size for analyzing the mean customer score with 90% confidence?

Why do we use a t-distribution to compute confidence intervals for population means?

A research doctor wanted to estimate the average total cholesterol level of general adult population. He took a random sample of 12 adults for blood test and obtained the following sample. Assume that total cholesterol level of adult population is normally distributed. Use these data to create a 95% confidence interval for the population mean total cholesterol level.                  175, 234, 189, 256, 170, 187, 192, 225, 245, 251, 195, 230   a) Find the sample mean and the standard deviation (round to two decimal places) b) 95% confidence interval for the population mean total cholesterol level (round to two decimal places)

Nestle Philippines wants to estimate the average annual milk consumption in a province. A random sample of 16 people resulted in an average annual consumption to be 60 gallons with a standard deviation of 20 gallons. Assume that the population distribution is normal. a) What is the value of the population mean? What is the best estimate for this value? b) Explain why we need to use the t distribution. What assumption(s) do we need to make? c) For a 90% confidence interval, what is the value of t? d) Develop the 90% confidence interval for the population mean. Interpret your results. Interpretation: e) Would it be reasonable to conclude that the population mean is 63 gallons?

A labor department wants to study mean age of all people in the civilian labor force. The average age of 49 randomly selected people in the civilian labor force is found to be 35.6 years. Assuming the population standard deviation is 11, what is the 95% confidence interval for true population mean?

Choose correct option and explain.

Consider the sample dataset : 2,4,5,9,10.    What is point estimate and sample standard deviation? What is margin of error at 95% confidence level? Calculate confidence intervals at 95% confidence level.