







A normal distribution problem 
20101202 

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 
20101125 

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 Tscores 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. 





Zscore 
20090325 

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. 





Finding the Raw Score for a Mean of 0 and Standard Deviation of 1 
20081002 

From Anita: A variable Y has a distribution of mean of Y =80 and standard deviation of Y=36. Find the values of A and B for transforming y*=A +BY so that mean of y* =0 and standard deviation of y*=1. Answered by Janice Cotcher. 





On which assignment did I do better 
20020517 

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 
20020121 

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. 

