Statistics

1. The mean and standard deviation of the grades of a group of students who took an economic exam  were 69 and 7, respectively. The grades have a mound-shaped distribution. According to the Empirical Rule,

   a) Approximately 68% of the grades were between which grade?

   b) Approximately what percentage of grades were between 55 and 76?

  1. 👍 0
  2. 👎 0
  3. 👁 272
  1. a. 68% are mean ± 1 SD.

    b. Z = (score-mean)/SD

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores (from Z = -2 to +1).

    1. 👍 0
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. stat

    for randomly selected adults, IQ scores are normally distributed with a standard deviation of 15. the scores of 14 randomly selected college students are listed below. use a 0.10 significance level to test the claim that the

  2. Statistics

    A group of statistics students decided to conduct a survey at their university to find the average (mean) amount of time students spent studying per week. Assuming a standard deviation of 3 hours, what is the required sample size

  3. Statistics

    A group of statistics students decided to conduct a survey at their university to find the average (mean) amount of time students spent studying per week. Assuming a standard deviation of 6 hours, what is the required sample size

  4. probability and statistics

    Suppose every student in your class got a score of 85% on an exam. What are the mean and standard deviation of those exam scores without doing any calculations? I want to say the mean is 100 and the standard deviation is 1 but I

  1. college

    Suppose that, for a certain exam, a teacher grades on a curve. It is known that the grades follow a normal distribution with a mean of 70 and a standard deviation of 7. There are 45 students in the class. How many students should

  2. elementary statistics

    A statistics professor is used to having a variance in his class grades of no more than 100. He feels that his current group of students is different, and so he examines a random sample of midterm grades (listed below). At 0.05

  3. Math

    The marks obtained by a number of students in a certain subject are approximately normally distributed with mean 65 and standard deviation 5. If 3 students are selected at random from this group, what is the probability that at

  4. statistics

    The scores on a national achievement test are normally distributed with a mean of 50 and a standard deviation of 10. Out of a group of 200 students, how many would you expect to score more than 70?

  1. Statistics

    28. A group of statistics students decided to conduct a survey at their university to find the average (mean) amount of time students spend studying per week. Based on a simple random sample, they surveyed 144 students. The

  2. Psychology

    Twenty students randomly assigned to an experimental group receive an instructional program; 30 in a control group do not. After 6 months, both groups are tested on their knowledge. The experimental group has a mean of 38 on the

  3. Statistics

    A group of 56 randomly selected students have a mean score of 30.8 and a standard deviation of ó = 4.5 on a placement test. Find a 95% confidence interval for the mean score, ì, of all students taking the test.

  4. statistics

    Three students take equivalent stress tests. Which is the highest relative score? a. A score of 144 on a test with a mean of 128 and a standard deviation of 34. b. A score of 90 on a test with a mean of 86 and a standard deviation

You can view more similar questions or ask a new question.