LAB 3



LAB 3 INSTRUCTIONS & QUESTIONS USING EXCEL 2007

NORMAL DISTRIBUTIONS

NAME_______________________LABTIME__________BLDG_____________

1. Open Excel from Microsoft Office 2007. Click on Office>Excel Options>Trust Center>Trust Center Settings>Macro Settings and select Enable all macros. Click OK and another OK.

2. Go to the Stat301T webpage, click on Lab Instruction, Questions and Data, open Lab 3 Instructions and Questions.

3. Save the Normal Table file to your home directory.

4. Open the Normal Table file.

5. You should get a yellow screen that says Probability Calculations. Click on Normal.

6. You should get a screen showing a normal curve with two z boxes below it.

7. You can fill in any z values in the boxes and the template will show the area between the two z values in blue. Also the percent of the entire area will be shown.

8. If you want to know the percent below a certain z value, use a lower value of -5. Likewise use an upper z value of 5 for percents above a given z value.

9. The standard normal density curve has a mean, µ = 0 and a standard deviation, σ = 1.0

10. Use the template to determine the percent of area between z = -2.3 and z = 2.3 ________________________ .

11. What percent is below -2.3?______________________

12. What percent is above -2.3?_____________________ .

13. By trial and error find the z value (2 decimal places) which is equivalent to the 1st quartile (has 25% below it, or as close as possible to 25%)___________________________ .

14. The z value for the 3rd quartile has the same value but the sign is positive.

15. Enter these two z values and record the percent area between them_____.

16. Other normal density curves require reduction of the boundary values to the equivalent z values using the formula z = ( x – µ ) / σ .

To go the other way: x = µ + z σ

17. SAT Verbal scores in 2000 followed approximately a normal distribution with mean, µ = 504 and standard deviation, σ = 111.

The shorthand designation for this is N( 504, 111).

18. Find the percent of SAT verbal scores which would be between 400 and 600. Convert the values 400 and 600 to their equivalent z values, (2 decimal places), enter them in the template and record the percent. ____________ .

19. Find the percent of SAT verbal scores which would be above 700 _________________.

20. Find the percent of SAT verbal scores which would be below 300 _________________.

21. Find the percent of SAT verbal scores which would be above 400 _________________ .

22. Find the percent of SAT verbal scores which would be between 300 and 400 ___________________ .

23. Use the z value for the 1st quartile ( from step 13 ) and the second formula in step 18 to calculate the 1st quartile for the distribution of SAT verbal scores __________________________ .

24. Repeat step 23 to find the 3rd quartile for the SAT verbal scores ___________________ .

25. Close the normal template.

26. Save your file.

Updated on 9-18-08

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