The outputs of 12 selected Keurig coffee makers are listed below. The quality control  needs the standard deviation to be low. Construct a 98% confidence interval for the  population standard deviation, σ.  11.85, 11.96, 11.9, 11.92, 12.01, 11.95, 11.96, 11.89, 11.97, 12.03, 11.88, 11.94

In a random sample of 17 people, the mean commute time to work was 30.2 minutes and the standard deviation was 7.1 minutes. Assume the population is normally distributed and use a t- distribution to construct a 95% confidence interval for the population mean y. What is the margin of error of y? Interpret the results.

The lifetimes of lightbulbs of a particular type are normally distributed with a mean of 400 hours and a standard deviation of 10 hours. What percentage of the bulbs have lifetimes between 380 hours and 420 hours?     99.7%     95%     68%     84%

In a random sample of ten cell​ phones, the mean full retail price was ​$433.00 and the standard deviation was ​$208.00. Assume the population is normally distributed and use the​ t-distribution to find the margin of error and construct a 99​% confidence interval for the population mean μ. Interpret the results.

A study is done to determine if students in the California state university (CSU) system take longer to graduate, on average, than students enrolled in private universities using the significant level of 5%. One hundred students from both the California state university system and private universities are surveyed. Suppose that from years of research, it is known that the population standard deviations are 1.5811 years for CSU and 1 year for private universities. The following data are collected. The California state university system students took on average 4.5 years with a standard deviation of 0.8. The private university students took on average 4.1 years with a standard deviation of 0.3. What is the decision rule of rejecting the null hypothesis

The ages of undergraduate students at two universities (one in the east and one in the west) are being compared.  Researchers want to know if there is a difference in the mean age of students at the two universities.  The population standard deviations are known. The following data shows the results of samples collected at each institution:              School Location       n (sample size)        sample mean ( )         population standard deviation              West                      33                           25.78                       6.29              East                       35                           23.16                       7.52   What is the value of the test statistic for the previous problem?  (Enter your answer as a positive value even if you calculated a negative test statistic value i.e. if you calculated -1.311 you should enter 1.311).  Round your answer to 3 decimal places.