Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
Mean/Z-Score Question/Probability...need help asap!?
The mean of a standardized statistics test is 82 with a standard deviation of 4. The test scores are normally distributed.
a. What is the probability that a person scores between 74 and 90?
b. What percent of people will score between 78 and 86?
c. What is the z-score associated with a test score of 75?
d. What does a z-score measure?
1 Answer
- cidyahLv 78 years agoFavorite Answer
a)
μ = 82
σ = 4
standardize x to z = (x - μ) / σ
P( 74 < x < 90) = P[( 74 - 82) / 4 < Z < ( 90 - 82) / 4]
P( -2 < Z < 2) = 0.9772 -0.0228 =0.9544
find the area below 2; find the area below -2; subtract.
(From Normal probability table)
b)
μ = 82
σ = 4
standardize x to z = (x - μ) / σ
P( 78 < x < 86) = P[( 78 - 82) / 4 < Z < ( 86 - 82) / 4]
P( -1 < Z < 1) = 0.8413 -0.1587 = 0.6826
find the area below 1; find the area below -1; subtract.
(From Normal probability table)
c)
(75-82)/4 = -7/4 = -1.75
d)
How many standard deviation from the mean a value is.
