Descriptive Stats
If the mean of a distribution is greater than its median, what is most likely the shape of the distribution?
Skewed right
When do we say that the design of a study is biased?
When certain outcomes are systematically favored.
A company claims that the number of defective items manufactured during each run of making 100 of their products is independent of the number from other runs and that the proportion of defectives is no more than 4%. Assume that the proportion of defectives for each run is .04. What is the probability that there will be no defectives on the next run?
.017
A alpha level of a test of significance is also equal to what?
The Probability of a Type I error
List the conditions for a t-test.
SRS; Normality n≥30; Independence N≥10n.
If the range of a set of data is 36, what is a reasonable estimate of the standard deviation?
6
What is the difference between an observational study and an experiment?
In an experiment, a treatment is imposed.
The number of sweatshirts a vendor sells daily has the following probability distribution:
x 0 1 2 3 4 5
p(x) 0.3 0.2 0.3 0.1 0.08 0.02
If each sweatshirt sells for $25, what is the expected daily total dollar amount taken in by the vendor from the sale of sweatshirts?
$38
Correct this statement: if the P-value of a test is greater than α, we accept the null hypothesis.
We fail to reject the null hypothesis
Name the conditions for a one-proportion z-test.
SRS;
np ≥ 10 and n(1 – p) ≥ 10;
10% condition
If the test scores of a class of 30 students have a mean of 75.6 and the test scores of another class of 24 students have a mean of 68.4, then the mean of the combined group is…
72.4
A research team wishes to compare performance in AP Statistics based on whether the students were taught using activity-based or traditional lecture methods. The final grades in AP Statistics for 500 students were collected. What is the population of interest?
All students taking AP Statistics
In a certain game, a fair die is rolled and a player gains 20 points if the die shows a “6.” If the die does not show a “6,” the player loses 3 points. If the die were to be rolled 100 times, what would be the expected total gain or loss for the player?
Gain of about 83
What is a type I error?
We reject the null hypothesis when we should not have
Name the conditions for Chi-square GOF test.
SRS;
All expected counts ≥ 5; Independence
Joey scored a 720 on the math portion of the SAT and Luke scored a 34 on the math portion of the ACT. Scores for each test are Normally distributed. The SAT has a mean of 580 and a standard deviation of 100, while the ACT has a mean of 26 with a standard deviation of 5. Who had the better relative performance?
Luke
Name three components for a valid experiment
Control, replication, and randomization
All bags entering a research facility are screened. Ninety-seven percent of the bags that contain forbidden material trigger an alarm. Fifteen percent of the bags that do not contain forbidden material also trigger the alarm. If 1 out of every 1,000 bags entering the building contains forbidden material, what is the probability that a bag that triggers the alarm will actually contain forbidden material
0.00643
Name two ways we can reduce the width of a confidence interval?
Increase sample size; reduce the confidence level
We want to run a test on a mean difference. What is the name of the test
Match pairs t-test
For a particular bivariate data set, r2 is found to be 0.64. Interpret this value
64% of the variation in y can be accounted for by least squares regression of y on x.
What is the purpose of a control group in an experiment?
To control the effect of lurking variables and to reduce bias
A student is taking a 5 question multiple choice test. Each question has 4 choices of answers. If a student randomly answers the questions find the probability that the student answers at least 4 questions correctly.
0.015625
A local news station reports that the 97% confidence interval for a candidate’s support was (43%, 48%). What does the phrase 97% confidence mean?
If we repeated this procedure many times, 97% of the resulting CI’s would contain the true population proportion
What is the order of graphs that we check if our sample size is not large enough?
Histogram, Boxplot, Normal Probability Plot