Suppose a particular outcome from a random event has a probability of 0.02. Whic

Question

Suppose a particular outcome from a random event has a probability of 0.02. Which of the following statements represent correct interpretations of this probability?

(a) The outcome will never happen. (b) The outcome will certainly happen two times out of every 100 trials. (c) The outcome is expected to happen about two times out of every 100 trials. (d) The outcome could happen, or it couldn’t, the chances of either result are the same. (e) None of the above.

A set of test scores are normally distributed. Their mean is 100 and standard deviation is 20. These scores are converted to standard normal z-scores. What would be the mean of this distribution?

(a) 0 (b) 1 (c) 50 (d) 100 (e) None of the above.

The USA Today AD Track (3/1/00) examined the effectiveness of the new ads involving the Pets.com Sock Puppet (which is now extinct). In particular, they conducted a nationwide poll of 428 adults who had seen the Pets.com ads and asked for their opinions. They found that 36% of the respondents said they liked the ads. If you wanted to cut the margin of error in half the next time you took a poll like this, what sample size would you need?

(a) One that is twice the size of what it was before. (b) One that is half the size of what it was before. (c) One that is a quarter the size of what it was before. (d) None of the above

Explanation / Answer

1)Suppose a particular outcome from a random event has a probability of 0.02. Which of the following statements represent correct interpretations of this probability?
Ans: (c) The outcome is expected to happen about two times out of every 100 trials.

2) A set of test scores are normally distributed. Their mean is 100 and standard deviation is 20. These scores are converted to standard normal z-scores. What would be the mean of this distribution
Ans: (a) 0

3) The USA Today AD Track (3/1/00) examined the effectiveness of the new ads involving the Pets.com Sock Puppet (which is now extinct). In particular, they conducted a nationwide poll of 428 adults who had seen the Pets.com ads and asked for their opinions. They found that 36% of the respondents said they liked the ads. If you wanted to cut the margin of error in half the next time you took a poll like this, what sample size would you need
Ans: (b) One that is half the size of what it was before.

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