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A normal distribution problem 2010-12-02
From Racquel:
I am stuck on this question. I am not sure if using the z score will help me get the answer I need. Here is the question?

The average length of time per week that students at this university spend on homework is normally distributed with a mean of 18 hours and a standard deviation of 3 hours. If Diane spends more time on homework each week than 75% of students, what is the minimum time she must spend?

Answered by Penny Nom.
t scores, z scores, standard scores and percentile ranks 2010-11-25
From Imogen:
I have an assignment that requires me to calculate the t scores, z scores, standard scores and percentile ranks of 3 children on a vocab task. I am struggling with how to calculate the correct T-scores for the children, my tutor has said that the sample has a mean of 50 and standard deviation of 10. So on a z- score of 2.0 (2 SD's from the mean) it would be 50 + 10+10 = T score of 70. However the Z- scores i have are not whole numbers so I am struggling with it, i have one that is 1.27 , another that is 0.47 and the last one is 0.80. If you could help me on how to calculate these to get T scores that would be great. Thanks.
Answered by Robert Dawson.
Z-score 2009-03-25
From Barb:
I am having trouble finding information on a z score and the conversion to the number of standard deviations a z value can be away from the mean. What exactly does that mean and what am I looking for? Help Please.
Answered by Harley Weston.
z-score 2008-07-23
From Sophia:
Indicate whether the factor influences the numerator or denominator of the z-score and determine whether the effect would be to increase the value of z(farther from zero) or decrease the value of z(closer to zero).
a. increase trhe sample size
b. increase the population standard deviation
c. increase the difference between the sample mean and the value of specified in the null hypothesis

Answered by Janice Cotcher.
z-score 2008-07-02
From Candace:
If a normal-shaped distribution has a mean of 80 and a standard deviation of 15 what is the z-score for M=84 for a sample of n=25 scores. Is this sample mean in the middle 95% of the distribution?
Answered by Harley Weston.
On which assignment did I do better 2002-05-17
From Denise:
I have 2 writing assignments in class. The first assignment, which had a mean of 10 and a standard deviation of 2, I got a score of 12. The second assignment had a mean of 18 and an s.d. of 3, I got a 21. I need to know which assignment did I do better, relative to my classmates?
Answered by Andrei Volodin.
Normal distribution 2002-01-21
From Danielle:
A teacher gave a test on which the students' marks were normally distributed, but the results were pathetic. The mean was 52% and the standart deviation was 12%. The teacher decided that the top 10% of the students should get A's, the next 20% should get B's, the next 40% should get C's, the next 20% should get D's, and the bottom 10% should get F's. To the nearest percent, what are the cutoff marks that will result in an A, B, C, D, and F?
Answered by Penny Nom.



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