Assignment:
Write TRUE or FALSE - all answrs must be at least 25 words
1. Class width = Upper limit of a class - Lower limit of the same class.
2. A class frequency may be equal to zero.
3. The data 9, 12, 18, 30, 25, 15, 8, 42, 29, 44, 31, 26 can be broken into 5 classes: 8-15, 16 - 23, 24 - 31, 32 - 39, 40 - 44. One of these classes is empty.
4. For a given data set, the mean and median are always nearly equal.
5. In the same set of data, two or more elements may have the same z score.
6. A negative z score is unusual.
7. For a set having only negative values, both the mean and standard deviation will be negative.
8. In a lottery, the more tickets you buy, the more chance you have to win the prize(s).
9. If you have 3 suits, 10 shirts, and 12 neckties, you can come to work each time in a different outfit during the whole year.
10. If in a probability distribution you got the sum of probabilities less than one, it may mean that you skipped some possible outcome/outcomes.
11. Health insurance policies are set up in such a way that a healthy person has a negative expected value, and a sickly person has a positive one.
12. If a distribution curve is bell-shaped, then this is a normal distribution.
13. If a distribution is normal, its curve is bell-shaped.
14. A normal distribution curve may be symmetric, left-skewed, or right-skewed.
15. Because the tails of the normal distribution curve are infinitely long, the total area under the curve is also infinite.
16. The higher the confidence level, the narrower the confidence interval.
17. A good way to decrease a confidence interval is to bring down the confidence level.
18. A good way to decrease a confidence interval is to increase the sample size.
19. Of these two formulas, 7-2 and 7-3, the first one never results in a greater sample size than the second formula.
20. A pre-election survey showed that Candidate A got 52%, and Candidate B got 48%. The margin of error is 3%. There is not enough reason for Candidate A to rejoice.
21. Supporting the null hypothesis would be possible only if we could prove it for 100% of all possible cases.
22. If the claim says that µ >200 and the sample mean is 215, we can say that the claim is true because it is obvious even without a formal test.
23. Values of F » 3 are evidence that .
24. A value of r = -0.851 shows that there is very little relationship between the two variables being compared.
25. A value of r = 0.158 shows that there is very little relationship between the two variables being compared.
26. If a correlation coefficient of r = 0.642 was found between two variables in a sample of paired data that were measured in feet, the value of r would change if the data were converted to inches and r was computed again.
27. More variation should be expected between larger samples, which is apparent by the chi-square distribution.
28. A test of independence can be used to determine a cause-and-effect link between the variables being studied.
29. Using the F distribution for a one-way ANOVA, the degrees of freedom for the denominator will always exceed the degrees of freedom for the numerator.
WHAT IS WRONG? - all answer must be at least 25 words!
1. A statistician is going to survey a sample of 50 people. He prepared a list of 50 random phone numbers generated by a computer. Next morning he came to work at 8:00 and began to make calls. By 11:00 a.m., his survey was done.
2. The United Nation declared that the world's six-billionth inhabitant was born on October 12, 1999 in Bosnia.
3. Jim Smart started a furniture business in December, 1998. During that month, his factory produced 50 tables. During the whole 1999, 1000 tables were made. In January 2000, Jim proudly announced, "During the last year we increased our production 20 times!"
4. You bought 10 lottery tickets. One of them won a prize. That means that the probability of winning a prize is 1/10.