STAT 121 Test Questions Verified Answers
Fill in the blank: The t-distribution with 8 degrees of freedom has ____________________
the standard Normal distribution.
the same center but is more spread out than
We use a t-distribution with n-1 degrees of freedom rather than the standard normal
distribution whenever
we are using s to estimate σ.
Fill in the blank: The t-distribution with 4 degrees of freedom is _______________________
the standard Normal distribution.
flatter and more spread out than
Standard error of x̄ refers to:
the estimate of the standard deviation of the sampling distribution of x
The test statistic 𝑡 = (x̄− 𝜇) /(𝑠 / √𝑛)
measures:
how many standard errors the observed x̄ is from the claimed parameter value μ0.
Whenever performing a one sample t procedure on means, we should check for
randomization and no outliers or strong skewness in the data.
A study was conducted on all small electrical appliances to determine whether any link could
be found between leukemia and appliance use. Statistically significant links were found
between only hair dryers and black-and-white televisions even though over 50 appliances
were tested. Wise consumers of statistical information would conclude that
because multiple tests were performed, the results are only suggestive, not
conclusive.
, Suppose you are testing the following hypotheses. What is the type I error for these
hypotheses? H0: Cake is not done versus Ha: Cake is done
To believe that the cake is done when it is still not done.
The margin of error in a confidence interval covers only which kind of errors?
errors due to random sampling
The purpose of a confidence interval is to provide
plausible values that a parameter could be.
What two things do we need in order to compute margin of error for a one-sample t-
confidence interval for μ?
Level of confidence and the standard error of x̄.
We want to test the hypotheses H0: μ = 50 versus Ha: μ > 50 to determine whether a new
variety of corn will yield more than 50 bushels per acre. We plan to sample 100 plots and
measure yield per acre on each plot. Assuming H0 is true and that σ = 5, describe the
sampling
distribution of x̄.
Unknown because we do not know the shape of the distribution of yield of corn.
Refer to the above question. Suppose x̄ = 50.15 bushels per acre. Graphically, what represents
the P-value?
The area under the sampling distribution of x̄ curve to the right of 50.15
Statistically significant is equivalent to all of the following except one. Which one is not
equivalent?
a) P-value < α.
b) The difference between the observed value of the statistic and the value of the
parameter as given in H0 is too large to attribute to just chance variation.
c) The probability of obtaining a sample statistic as extreme or more extreme than
Fill in the blank: The t-distribution with 8 degrees of freedom has ____________________
the standard Normal distribution.
the same center but is more spread out than
We use a t-distribution with n-1 degrees of freedom rather than the standard normal
distribution whenever
we are using s to estimate σ.
Fill in the blank: The t-distribution with 4 degrees of freedom is _______________________
the standard Normal distribution.
flatter and more spread out than
Standard error of x̄ refers to:
the estimate of the standard deviation of the sampling distribution of x
The test statistic 𝑡 = (x̄− 𝜇) /(𝑠 / √𝑛)
measures:
how many standard errors the observed x̄ is from the claimed parameter value μ0.
Whenever performing a one sample t procedure on means, we should check for
randomization and no outliers or strong skewness in the data.
A study was conducted on all small electrical appliances to determine whether any link could
be found between leukemia and appliance use. Statistically significant links were found
between only hair dryers and black-and-white televisions even though over 50 appliances
were tested. Wise consumers of statistical information would conclude that
because multiple tests were performed, the results are only suggestive, not
conclusive.
, Suppose you are testing the following hypotheses. What is the type I error for these
hypotheses? H0: Cake is not done versus Ha: Cake is done
To believe that the cake is done when it is still not done.
The margin of error in a confidence interval covers only which kind of errors?
errors due to random sampling
The purpose of a confidence interval is to provide
plausible values that a parameter could be.
What two things do we need in order to compute margin of error for a one-sample t-
confidence interval for μ?
Level of confidence and the standard error of x̄.
We want to test the hypotheses H0: μ = 50 versus Ha: μ > 50 to determine whether a new
variety of corn will yield more than 50 bushels per acre. We plan to sample 100 plots and
measure yield per acre on each plot. Assuming H0 is true and that σ = 5, describe the
sampling
distribution of x̄.
Unknown because we do not know the shape of the distribution of yield of corn.
Refer to the above question. Suppose x̄ = 50.15 bushels per acre. Graphically, what represents
the P-value?
The area under the sampling distribution of x̄ curve to the right of 50.15
Statistically significant is equivalent to all of the following except one. Which one is not
equivalent?
a) P-value < α.
b) The difference between the observed value of the statistic and the value of the
parameter as given in H0 is too large to attribute to just chance variation.
c) The probability of obtaining a sample statistic as extreme or more extreme than
