28. Z is a standard normal random variable. The P(-1.96  Z  -1.4) equals
a. 0.8942
b. 0.0558
c. 0.475
d. 0.4192

29. The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. The probability of a player weighing less than 250 pounds is
a. 0.4772
b. 0.9772
c. 0.0528
d. 0.5000

31. A population has a standard deviation of 16. If a sample of size 64 is selected from this population, what is the probability that the sample mean will be within 2 of the population mean?
a. 0.6826
b. 0.3413
c. -0.6826
d. Since the mean is not given, there is no answer to this question.

Solution Summary

The solution is provided in an attachment and includes explanations to the multiple choice answers and references.

In a manufacturing process a machine produces bolts that have an average length of 3 inches with a variance of .03. If we randomly select three bolts from this process: What is the standard deviation of the sampling distribution of the sample mean?

If the mean exam score in a class of 30 students is an 80 out of 100 and the standard deviation on the exam is 15, what percentage of students earned between 65 and 95, assuming a normal distribution of grades on the exam? How alarmed should a student with a score of 49 be with his grade?

What are the characteristics of a standard normal distribution? Can two distributions with the same mean and different standard distributions be considered normal? How might you determine if a distribution is normal from its graphical representation?

1.) Test one: mean is 80 and standard deviation is 9. Mark scores 91
Test two: mean is 77 and standard deviation is 6. Mark score 87
Find the percentile for all
Which test Mark did better? Why?
2.) What is the the standard deviation for IQ tests? If someone's IQ is 140, how many standard deviation is it above the

Determine the mean and the standard deviation of the following frequency distribution.
CLASS FREQUENCY
0 UP TO 5 2
5 UP TO 10 7
10 UP TO 15 12
15 UP TO 20 6
20 UP TO 25

When we move from the basic normal distribution to the sampling distribution of the mean we substitute the standard error of the mean for the standard deviation when we make the conversion to the standardized normal distribution. Why do we use the standard error of the mean in this case? And how does using the standard error aff

The score distribution shown in the table is for all students who took a yearly AP stats exam.
Score Percent of Students
5 13.3
2 21.9
3 24.9
2 17.8
1 22.1
Find the mean AND standard deviation:

Random samples of size 17 are taken from a population that has 200 elements, a mean of 36, and a standard deviation of 8. The mean and the standard deviation of the sampling distribution of the sample means are:

In what ways is the t distribution similar to the standard normal distribution?
In what ways is the t distribution different from the standard normal distribution?
How does the formula for the t test differ from the formula for the z test?

A frequency distribution is shown below. Complete parts (a) through (e).
The number of dogs per household in a small town
Dogs 0 1 2 3 4 5
Households 1157 417 168 45 26 16
a) Use the frequency distribution to construct a probability distribution.
X