# statistics

Scores on a test have a mean of 66 and Q3 of 81. The scores have a distribution that is approximately normal. Find the standard deviation. Round your answer to the nearest tenth.

1. 👍
2. 👎
3. 👁
1. Q3 = 75 percentile

In a table in the back of your stat book labeled something like "areas under normal distribution," find the Z score equivalent. Put value in formula below.

Z = (x - μ)/ SD = (81-66)/SD

Solve for SD.

1. 👍
2. 👎
2. (81-66)/SD = 0.67(z score of 0.75)
15/SD= 0.67
15/0.67
SD=22.3880

1. 👍
2. 👎

## Similar Questions

1. ### math new question

15. Which of the following would best display information in a frequency table that has been divided into categories? bar graph**** pictograph circle graph histogram 14. The mean of a set of four test scores is 85. If three of the

2. ### Statistics

5. Scores on a recent national statistics exam were normally distributed with a mean of 80 and a standard deviation of 6. a. What is the probability that a randomly selected exam will have a score of at least 71? b. What

3. ### Math

The mean of a set of four test scores is 85. If three of the test scores are 81,83, and 85, what is the fourth test score? A. 89 B. 87 C. 91 D. 85 Is the answer A? Thank you

4. ### Statistics

Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the following quantities: Suggest you make a drawing and label first… a. Percentage of

1. ### Math-statistics

Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the following quantiles: a.percentage of scores less than 100 b. relative frequency of

2. ### Statistics... I need help

. Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the following quantities: (Hint: Make a drawing and label first) a. Percentage of scores

3. ### Statistics

The scores on a math test are normally distributed. if the mean is 72 and the standard deviation is six, what is the range of 98% of the scores?

4. ### Stats

A sociology professor assigns letter grades on a test according to the following scheme. A: Top 14% of scores B: scores below the top 14% and above the bottom 55% C: scores below the top 45% and above the bottom 17% D: scores

1. ### Word Problem

A math teacher gives two different tests to measure students' aptitude for math. Scores on the first test are normally distributed with a mean of 25 and a standard deviation of 4.6. Scores on the second test are normally

2. ### Math 9

On the first 6 tests in her social studies course, Jerelyn’s scores were 92 78 86 92 95 and 91. determine the median and the mode of her scores. If Jerelyn took a seventh test and raised the mean of her scores exactly 1 point,

3. ### statistics

the admissions policy at a certain university requires that incoming students score in the upper 20% on a standardized test. if the mean score on the test is 510 and the standard deviation of the scores is 80, what is the minimum

4. ### statistics

Nine students took the SAT. Their scores are listed below. Later on, they read a book on test preparation and retook the SAT. Their new scores are listed below. Construct a 95% confidence interval for µ d (the true mean