Quiz STAT
Danyah
practice_questions_sp15_key.docSTAT Practice Questions I
Questions 1-5: In 5 trials of flipping a coin, assuming the chance of getting a tail is 50%, what is the probability of:
1. Getting 2 tails? P (X=2) = P(X ≤2) – P (X≤ 1) = 0.500 – 0.188= 0.312
2. Getting less than 2 tails? P (X<2) = P (X≤ 1) = 0.188
3. Getting 3 or less tails? P (X≤3) = 0.813
4. Getting 2 or more tails? P (X ≥ 2) = 1 – P (X≤ 1) = 1- 0.188= 0.812
5. Getting more than 6 tails? P (X > 6) = 0
Questions 6-15: In a given population, the average blood sugar level was found to be 100 with a standard deviation of 10, find the following probabilities:
6. Greater than or equal to 110 [ P= 0.1578)
7. Between 91 and 106 [ P = 0.5417]
8. Less than or equal to 88 [ P = 0.1151]
9. Less than 80 and greater than 100 [ P = 0.5228]
10. What z-score would be for the upper 10 % of the blood sugar level?
[Z = 1.28]
11. What would be the cut-off values of blood sugar levels for the middle 90 % of the population? [ X1 = 83.5 & X2=116.5]
12. A z-score of 1.59 would correspond to what blood sugar level?
[X = (1.59*10) + 100 = 115.9]
13. What would be the z-score for representing a blood sugar level of 120 and less?
[Z = (120 -100) / 10 = 2]
14. What z-score would correspond to the cutoff point for the lowest 60 % of the population?
[Z = 0.25]
15. What blood sugar level would be used to put someone in the top 70 % of the population?
[Z = - 0.52 and X= (-0.52*10) + 100 = 94.8]
Questions 16-20: Use the table below to answer the following questions.
|
|
Developed cold |
Total |
|
|
|
Yes |
No |
|
|
High vitamin C intake |
21 |
189 |
210 |
|
Medium vitamin C intake |
40 |
55 |
95 |
|
Low vitamin C intake |
75 |
20 |
95 |
|
Total |
136 |
264 |
400 |
16. What is the probability of NOT developing cold? 264/400 = 0.660
17. What is the probability of Low vitamin C intake? 95/400 = 0.238
18. What is the probability of low vitamin C intake among those that have developed cold? 75/136 = 0.551
19. What is the probability of low or high vitamin C intake? (210/400) + (95/400)= 305/400 = 0.763
20. What is the probability of low vitamin C intake or developing cold?
(95/400) + (136/400) – (75/400) = 156 /400 = 0.390
Questions 21-23: Use the table below to answer the following questions.
|
Number of medical tests performed on emergency patients |
Number of patients |
|
0 |
12 |
|
1 |
8 |
|
2 |
2 |
|
3 |
3 |
|
4 or more |
5 |
|
Total |
30 |
If a patient is selected at random, find these probabilities
21. The patient has exactly two tests done. 2/30 = 0.067
22. The patient has at least two tests done. 10/30 = 0.333
23. The patient has had one or two tests done. 10/30 = 0.333
