1. Assuming that the following sample is taken from a normal distribution, compute the 90% confidence interval for the population mean.

Dataset:

67.2

82.2

59.7

54.9

77.7

48.1

95.2

63.8

96.7

87

1. A telecommunication company wants to estimate the mean length of time (in minutes) that 18- to 24- year-olds spend text messaging each day. In a random sample of fifty-eight 18- to 24-year-olds, the mean length of time spent text messaging was 29 minutes. From past studies, the company assumes that is 4.5 minutes and that the population of times is normally distributed.
   1. Compute a 99% confidence interval for the population mean time that 18- to 24-year-olds spend text messaging each day.
   2. Interpret the confidence interval found in part a.
   3. What does the phrase "99% confidence" refer to in this context?

1.The following table shows the results of a survey in which 1017 adults from the United States, 1060 adults from Italy, and 1126 adults from Great Britain were asked the question: "Does climate change pose a large threat to the world?"

Country	Percentage That Responded "Yes"
United States	27%
Italy	49%
Great Britain	31%

Construct and interpret a 98% confidence interval for

1. The population proportion of adults from the United States who say that climate change poses a large threat to the world.
2. The population proportion of adults from Italy who say that climate change poses a large threat to the world.
3. The population proportion of adults from Great Britain who say that climate change poses a large threat to the world.
4. To compare the braking distance for two types of tires, a safety engineer conducts 45 braking tests for each type. The results of the tests are given below.

Tire Type	Mean	Standard Deviation
Tire A	42 feet	2.9 feet
Tire B	45 feet	3.1 feet

1. Construct a 98% confidence interval for the difference in the population mean braking distance of the two tire types.
2. Based on the interval in part a., does it appear that there is a statistically significant difference between the two population means? Explain.