Some researchers are doing a two-mean pooled t-test. They have two samples with sizes n1=17 and n2=21. The population standard deviations are unknown but assumed to be equal, so the sample standard deviations are found and used to calculate a pooled standard deviation, sp. For sample 1: s1=9.8 and x¯1=30 For sample 2: s2=10.5 and x¯2=27 What are the test statistic (t) and the degrees of freedom to perform this test? Select the correct answer below:

On an intelligence​ test, the mean number of raw items correct is 236 and the standard deviation is 39. What are the raw​ (actual) scores on the test for people with IQs of​ (a) 119​, ​(b) 81​, and​ (c)100​? To do this​ problem, first figure the Z score for the particular IQ​ score; then use that Z score to find the raw score. Note that IQ scores have a mean of 100 and a standard deviation of 15.   ​(a) What is the raw​ (actual) score on the test for people with an IQ of 119​?

Researchers measured the data speeds for a particular smartphone carrier at 50 airports. The highest speed measured was 75.2 Mbps. The complete list of 50 data speeds has a mean of x= 15.49 Mbps and a standard deviation of s = 18.83Mbps.

Deanna is the principal at a Midwestern middle school and wants to know the average IQ of all female, seventh grade students.  She does not know anything about what the population distribution looks like.  She took a simple random sample of 31 seventh-grade girls in her school and found the average IQ score in her sample was 105.8 and the standard deviation was 15. Using the sample standard deviation above to estimate the population standard deviation, what is the minimum sample size needed for a 99.5% confidence interval to have a margin of error of no more than 2.3?

The salaries of professional baseball players are heavily skewed right with a mean of $3.2 million and a standard deviation of $2 million. The salaries of professional football players are also heavily skewed right with a mean of $1.9 million and a standard deviation of $1.5 million. A random sample of 40 baseball players’ salaries and 35 football players’ salaries is selected. The mean salary is determined for both samples. Let  represent the difference in the mean salaries for baseball and football players. Which of the following represents the shape of the sampling distribution for ? skewed right since the populations are both right skewed skewed right since the differences in salaries cannot be negative approximately Normal since both sample sizes are greater than 30 approximately Normal since the sum of the sample sizes is greater than 30

Researchers measured the data speeds for a particular smartphone carrier at 50 airports. The highest speed measured was 77.8 Mbps. The complete list of 50 data speeds has a mean of x= 16.56 Mbps. And a standard deviation of s= 35.08 Mbps. What is the difference between carriers highest data speed and the mean of all 50 states. How many standard deviations is that?

A population of scores has a mean of 56. In this population, a raw score of 40 corresponds to a z score of -4. What is the population standard deviation?