Sampling Distributions Stats

At a particular college, 78% of all students are receiving some kind of financial aid.The school newspaper selects a random sample of 100 students and 72% of the respondents say they are receiving some sort of financial aid. Which of the following is true?

•  78% is a population and 72% is a sample.
• 72% is a population and 78% is a sample
• 78% is a parameter and 72% is a statistic
• 72% is a parameter and 78% is a statistic

Increasing the sample size of an opinion poll will reduce the

• bias of the estimates made from the data collected in the poll.
• variability of the estimates made from the data collected in the poll.
• variability of opinions in the sample.
• variability of opinions in the population.

A statistic is an unbiased estimator of a parameter when

• the statistic is calculated from a random sample.
• in many samples, the values of the statistic are very close to the value of the parameter.
•  in a single sample, the value of the statistic is equal to the value of the parameter
• in many samples, the values of the statistic are centered at the value of the parameter.

The mean and standard deviation of a population are 200 and 20, respectively. Sample size is 25. 
What is the mean of the sampling distribution?

• 200
• 16
• 25
• 4

The mean and standard deviation of a population are 200 and 20, respectively. Sample size is 25. 
What is the standard error of the sampling distribution?

• 200
• 16
• 25
• 4

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting one data value less than 190?

• 69%
• 42%
• 31%
• 58%

The mean and standard deviation of a population are 200 and 20, respectively. 
What is the probability of selecting 25 data values with a mean less than 190?

• 69%
• 0.6%
• 31%
• 99%

28% of all Woodrow students believe Monday will be snow day. You take a sample of 50 students and find that 15 of them believe Monday will be a snow day. What is the probability of getting a sample of size 50 that has 15 or more students who believe Monday will be a snow day? 

• 0.376
• Cannot be determined because the distribution of the sample proportion of samples of size 50 is not normal
• 0.624
• 0.99999

A z-score tells you...

• the standard deviation of a sampling distribution.
• the original raw score on which it is based.
• if the distribution it comes from is normal.
• how many standard deviations away from the mean a score lies.

What is the standard deviation of the distribution?

• 1010
• 20
• 60
• √20