1. Using the Calculator for Normal Distributions

2. Standard Normal Go to 2nd Distribution Find #2 – Normalcdf
Key stroke is
Normalcdf(Begin, end)
If standardized, then mean & st. deviation do not have to be given.

3. Find P(1.1<z<1.89) Press: Normalcdf (1.1, 1.89) enter
You should get
Check By chart method:
– =

4. To represent infinity we use
1E99 (1X10^99) for positive infinity
-1E99 (-1x10^99) for negative infinity
Represent in notation with ∞

5. Find: P(z<2.07)

6. Find: P(z>0.12)

7. Try the following
P(z < -1.23)
P(-1.2<z<2.05)
P(z>1.23)

8. Average age of a student is 20 with standard deviation of 2. 1 years
Average age 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?

9. 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?

10. 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?

11. The mean time to run a race is 6
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?

12. Finding a percentile….
Use Invnorm(%) to get the z-score

13. The mean score on a test is 70 with  = 3
The mean score on a test is 70 with  = 3. What’s the cutoff score for the 90th percentile?

14. If the mean test score is 88 with standard deviation of 2, find the cutoff scores for the middle 40%.

15. So if the mean is 34 and you know that 78% scored less than 36, what’s the standard deviation?

16. If 28% scored less than 36 on a test, and 87% scored more than 34, what’s the mean and the standard deviation?

17. Homework
Worksheet