Using the Calculator for Normal Distributions Standard Normal
Using the Calculator for Normal Distributions
Standard Normal n Go to 2 nd Distribution Find #2 – Normalcdf n Key stroke is n Normalcdf(Begin, end) n If standardized, then mean & st. deviation do not have to be given.
Find P(1. 1<z<1. 89) n Press: Normalcdf (1. 1, 1. 89) enter n You should get 0. 1063 n Check By chart method: 0. 9706 – 0. 8643 = 0. 1063
To represent infinity we use n 1 E 99 (1 X 10^99) for positive infinity n -1 E 99 (-1 x 10^99) for negative infinity n Represent in notation with ∞
Find: P(z<2. 07)
Find: P(z>0. 12)
Try the following n P(z < -1. 23) n P(-1. 2<z<2. 05) n P(z>1. 23)
n Average of a student is 20 with standard deviation of 2. 1 years. What’s the probability that a student’s age is more than 23?
A professor can grade an average of 12 papers per day with a standard deviation of 1. 8 papers. What is the probability that he can grade between 10 and 13 papers?
The mean time to finish a test is 38 minutes with a standard deviation of 4. 8 minutes. What’s the probability that a person takes more than 45 minutes to finish the test?
The mean time to run a race is 6. 7 minutes with a standard deviation of 0. 37 minutes. Find the probability that it took less than between 6. 5 and 6. 8 minutes?
Finding a percentile…. n Use Invnorm(%) to get the z-score
The mean score on a test is 70 with = 3. What’s the cutoff score for the 90 th percentile?
If the mean test score is 88 with standard deviation of 2, find the cutoff scores for the middle 40%.
So if the mean is 34 and you know that 78% scored less than 36, what’s the standard deviation?
If 28% scored less than 36 on a test, and 87% scored more than 34, what’s the mean and the standard deviation?
Homework n Worksheet
- Slides: 17