(a) Use a calculator with mean and standard deviation keys to find x and s. (Round your answers to four decimal places.) (b) Compute a 90% confidence interval for the population mean u of home run percentages for all professional baseball players. Hint: If you use the Student's t distribution table, be sure to use the closest d.f. that is smaller. (Round your answers to two decimal places.) lower limit upper limit (c) Compute a 99% confidence interval for the population mean u of home run percentages for all professional baseball players. (Round your answers to two decimal places.) lower limit upper limit

The distribution of study times for first-year students follow a Normal distribution with a standard deviation σ = 48 minutes. Suppose a sample of 344 students found that the mean study time for these students was x¯= 170 minutes per week. Use this to find a 94.38% confidence interval to estimate the mean study time for all students. We are 94.38% confident that the mean study time for first-year students is between the following ( answer) minutes and  ( answer) minutes. The answer needs to be the mean study time for first-year students is between what amount of minutes and the following minutes.

Assume that adults have IQ scores that are normally distributed with a mean of 104.5 and a standard deviation 19.1. Find the first quartile Q,, which is the IQ score separating the bottom 25% from the top 75%. (Hint: Draw a graph. The first quartile is (Type an integer or decimal rounded to one decimal place as needed.)

## In a survey of adults with diabetes, the average body mass index (BMI) in a sample of 1938 women was 32.2 with a standard deviation of 0.03. The BMI in a sample of 1555 men was 30.4, with a standard deviation of 0.06. Construct a 92% confidence interval for the difference in the mean BMI between women and men with diabetes,  INTERPRET THE RESULTS. DOES THE CONFIDENCE INTERVAL CONTRADICT THE CLAIM THAT THE MEAN BMI IS THE SAME FOR BOTH MEN AND WOMEN WITH DIABETES?

The mayor is interested in finding a 90% confidence interval for the mean number of pounds of trash per person per week that is generated in the city. The study included 212 residents whose mean number of pounds of trash generated per person per week was 37.9 pounds and the standard deviation was 7.7 pounds. Round answers to 3 decimal places where possible. b. With 90% confidence the population mean number of pounds per person per week is between _______ and  ________ pounds. c. If many groups of 212 randomly selected members are studied, then a different confidence interval would be produced from each group. About __________ percent of these confidence intervals will contain the true population mean number of pounds of trash generated per person per week and about ____________ percent will not contain the true population mean number of pounds of trash generated per person per week.

Assume that adults have IQ scores that are normally distributed with a mean of 100.2 and a standard deviation 20.9. Find the first quartile Q₁, which is the IQ score separating the bottom 25% from the top 75%. (Hint: Draw a graph.) The first quartile is (Type an integer or decimal rounded to one decimal place as needed.)

Assume that adults have IQ scores that are normally distributed with a mean of 102.9 and a standard deviation 19.4. Find the first quartile Q,, which is the IQ score separating the bottom 25% from the top 75%. (Hint: Draw a graph.) The first quartile is Type an integer or decimal rounded to one decimal place as needed.)

Calcium levels in people are normally distributed with a mean of 9.7 mgdL and a standard deviation of 0.5 mgdL . Individuals with calcium levels in the bottom 10% of the population are considered to have low calcium levels. Find the calcium level that is the borderline between low calcium levels and those not considered low. Carry your intermediate computations to at least four decimal places. Round your answer to one decimal place.

A researcher is interested in finding a 90% confidence interval for the mean number of times per day that college students text. The study included 149 students who averaged 34.2 texts per day. The standard deviation was 18.6 texts. Round to 3 decimals. b. With 90% confidence the population mean number of texts per day is between _______ and ________ texts a day.

Lengths of pregnancies are normally distributed with a mean of 268 days and a standard deviation of 13 days. A baby is considered premature if the pregnancy length is at or below the third percentile (P3) of all pregnancy lengths. Find the length of pregnancy in days that separates the premature babies from those that are not considered premature. Round to the nearest integer.