stats final

a 95% confidence interval is wider than a 90% confidence interval if all else remains the same a. true b. false

a

a large p-value means you have little evidence against Ho a. true b. false

a

as population standard deviation increases, the margin of error: a. increases b. decreases c. does not change

a

if X does not have a normal distribution, which of the following is true about the shape(distribution) of the random variable x-bar? a. x-bar is approximately normal if n>30 b. x-bar is exactly normal if n>30 c. x-bar is approximately normal for any n d. x-bar is exactly normal for any n

a

the smaller alpha gets, the harder it is to reject Ho a. true b. false

a

if X and Y are independent, then the variance of X-Y= Variance of X - Variance of Y a. true b. false

b

if X has a continuos uniform distribution on the interval (0,5), what is the 25th percentile for X? a. .25 b. 1.25 c. 25% d. none of the above

b

if you switch X and Y the sign of the correlation changes a. true b. false

b

X has some unknown distribution. What do we know about the distribution of XBAR? a it has an exact normal distribution if the sample size n is large enough b. it has an approximate normal distribution for any sample size n c. it has an approximate normal distribution if the sample size n is large enough d. since the distribution of X is unknown, the distribution of XBAR is also unknown

c

suppose you take a random sample of size n and look at the average x-bar. As n increases, which of the following statement is true about the mean of X-bar? a. it increases b. it decreases c. it stays the same

c

the formula for a confidence interval for p involves a z-value. Why is this?? (assume n is large) a. because the original distribution was a normal distribution b. because you always use Z in any confidence interval c. because of the CLT d. all of the above

c

the set of all possible sample means for all possible samples of size n from the population is known as the: a. population probability distribution of X b. sample mean of the population of X c. sampling distribution of X d. not enough information to tell

c

which of the following is true about the mean of the random variable x-bar as n increases? a. the mean of x-bar decreases b. the mean of x-bar increases c. the mean of x-bar stays the same d. not enough information to tell

c

which of the following is true about the standard error of the random variable x-bar as n increases? a. the standard error of x-bar increases b. the standard error of x-bar stays the same c. the standard error of x-bar decreases d. not enough information to tell

c

if X has a normal distribution, when does X BAR also have a normal distribution? a. the CLT theorem is needed; n has to be large b. the CLT is needed; n can be any size c. the CLT is not needed; n has to be large d. the CLT is not needed; n can be any size

d

if x has a normal distribution, which of the following is true about the shape (distribution) of the random variable x-bar? a. x-bar is approximately normal if n>30 b. x-bar is exactly normal if n>30 c. x-bar is approximately normal for any n d. x-bar is exactly normal for any n

d

the normal distribution is used to approximate a binomial distribution only if: a. the sample size n is greater than 30 b. the population proportion p is close to .50 c. the underlying population is normal d. np and n(1-p) are both greater than or equal to 10

d

where is the 10th percentile of the z distribution? a. .10 b. .90 c. 1.28 d. -1.28

d

if X has a continuous uniform distribution on the interval (50,100), then what is f(75)? a. 1/50 b. 1/100

a

suppose you have a confidence interval for the population mean. If the population standard deviation were to increase ( and everything stayed the same) then the margin of error for your confidence interval would a. increase b. decrease c. not change

a

the CLT is important in statistics because it says: a. the distribution of a-bar is approximately normal, no matter what the distribution of X is, as long as n is large enough b. the distribution of x-bar is approximately normal, no matter what the distribution of X is, and no matter what the sample size it c. the distribution of X-bar is normal if the distribution of X is normal

a

the CLT only applies to the shape of the distribution of X-bar, not to its mean or standard error a. true b. false

a

the central limit theorem is important in statistics because: a. it says for n greater than or equal to 30, and any distribution thats not normal, the sampling distribution of X-bar is approximately normal b. it says for any sample size and any distribution that's not normal, the sampling distribution of x-bar is approximately normal c. it says for n greater than or equal to 30 and any distribution that's not normal, the sampling distribution of x-bar is exactly normal d. it says for any sample size, if X has a normal distribution, then the sampling distribution of x-bar is normal

a

there is a 100% chance that your sample mean lies within your 95% confidence interval a. true b. false

a

we use statistics to estimate population parameters, not the other war around d. true b. false

a

what type of distribution is normal a. continous b. discrete

a

if X is a continuous random variable, which of the following condition does NOT need to be checked to verify that f(x) is a legitimate probability distribution function? a. f(x) must be greater than or equal to 0 b. f(x) must be less than or equal to 1 c. f(x) must integrate to 1 d. all of the above must be checked

b

if you increase n, what happens to the margin of error of your confidence interval for p? a. it increases b. it decreases c. it stays the same d. not enough information to tell

b

the mean of x is equal to X BAR a. true b. false

b

the units of r, the correlation coefficient, are the same as the x-variable a. true b. false

b

which of the following describes the relationship between parameters and statistics? a. we use parameters to estimate or test statistics b. we use statistics to estimate of test parameters c. statistics and parameters are the same thing

b

which of the following would increase the margin of error? a. decrease the standard deviation b. increase the confidence c. increase the sample size

b

if the correlation coefficient r, between two variables is 0, we can conclude that there is no relationship between the two variables a. true b. false

b

if you are not able to prove the alternative hypothesis, this mean the null hypothesis is correct a. true b. false

b

A P-value in hypothesis testing means the same thing as the sample proportion a. true b. false

b

a binomial random variable is what type of random variable ? a. continous b. discrete

b

is P-hat the sample proportion of the population proportion?

sample