MD 2 True or False

Question 1

1. To eliminate bias one should use random sampling.

Answer 1

T: Random sampling eliminates bias

Question 2

2. Random sampling makes the sample data subject to laws of probability.

Answer 2

T: Random sampling subjects data to the laws of probabliliy

Question 3

3. Two variables in a study are said to be confounded if one cannot separate their effects on a response variable.

Answer 3

T: Confounding variables cannot separate their effects on a response variable

Question 4

4. In general, non-probability samples are less biased than probability samples.

Answer 4

F: Non-Probability samples are MORE biased that probability samples

Question 5

5. The effects of lurking variables including the placebo effect can be controlled by comparing two or more treatments.

Answer 5

T: Comparing two or more treatments can control effects of lurking variables ie placebo

Question 6

6. By assigning multiple subjects to each treatment in an experiment, the variability among the subjects will average out.

Answer 6

T: Adding more subjects to a treatments will average out the variablility

Question 7

7. If two events are disjoint (mutually exclusive), they are also statistically independent.

Answer 7

F: Disjoint events can still be statistically dependent

Question 8

8. If events A and B are independent, P(A|B) = P(B|A).

Answer 8

F: If A and B are independent P(A & B)= P(A) X P(B)

Question 9

9. If events A and B are disjoint (mutually exclusive), P(A U B) = P(A) + P(B).

Answer 9

T: the probability of P given B is the sum of P(A) plus P(B)

Question 10

10. The probability of a continuous random variable is defined only for an interval or a collection of intervals.

Answer 10

T: C.R.V have a probability defined only for an interval P(.5<1.5)

Question 11

11. A Normal distribution can be used to approximate a Binomial distribution when the number of observations are large enough such that np>10 and n(1-p)>10

Answer 11

T: Idk Learn binomial distrib..

Question 12

12. An unknown population parameter is a random variable.

Answer 12

F: An unknown population parameter is not a random variable!

Question 13

13. A sample statistic is a random variable.

Answer 13

T: A sample stat is a r.v

Question 14

14. An unbiased statistic has no variability.

Answer 14

F: All statistics have variability

Question 15

15. To reduce the variability of a statistic, one should use a larger sample.

Answer 15

T: The larger the sample the closer to average you have, therefore less variability

Question 16

16. The variability of a statistic is not affected by the size of the population as long as the population is at least 100 times larger than the sample.

Answer 16

T: With a pop 100x larger than the sample it doesnt matter after that big

Question 17

17. Consider an SRS drawn from a large population. As the sample size increases, the standard deviation of the sample mean also increases.

Answer 17

F: As the sample size for a SRS increase the stdev goes down because of the law of averages

Question 18

18. Consider an SRS drawn from a large non-Normal population. When the sample size is large, the sample mean has approximately a Normal distribution regardless of the population distribution.

Answer 18

T: If the sample size is large enough it will always have a normal distribution

Question 19

19. The standard deviation of a sample mean is always less than or equal to the population standard deviation.

Answer 19

T: A stdev of a sample will always be closer to the average than the sample pop.

Question 20

20. A confidence level gives the probability that the confidence interval will capture the true parameter value in repeated samples.

Answer 20

T: That is the definition of confidence interval

Question 21

21. As the sample size increases, the width of a confidence interval increases.

Answer 21

F: As the sample size increases, the confidence interval gets smaller because they are closer to the mean.

Question 22

22. As the confidence level increases, the margin of error associated with a confidence interval decreases.

Answer 22

F: As the confidence interval increases the margin of error goes up as well!