exploratory analysis
What is a measure of center?
Median or Mean
What conditions must be checked for a z-interval?
Random, Independent, Normal?
The chance of any outcome will always be a number between 0 and 1 that describes the proportion of times the outcome will occur in a very long series of repetitions.
When can you use a sample size of 20 for a t-test?
When there are no apparent outliers or skewness.
What is the Central Limit Theorem?
Spread, Outliers, Center, Shape
What are the conditions that must be checked for a linear regression test?
linear, independent, normal, equal variance, random
Define a discrete random variable.
A fixed set of possible values with gaps between.
What test would you conduct for the following scenario:
When accounting firms audit the company's financial records for fraud, they often use a test based on Benford's Law, which states that the distribution of first digits in many real-life sources of data is not uniform. When there is no fraud, about 30.1% of the numbers in financial records begin with the digit 1. However, the proportion of first digits that are 1 is significantly different from 0.301 in a random sample of records at a company and so the company conducts a study to test this. Suppose that a random sample of 300 expenses from a company's financial records result in only 68 expenses that begin with digit 1.
One-proportion z-test
What does mutually exclusive mean?
Two events are mutually exclusive (disjoint) if they have no outcomes in common and can never occur together.
Which of the following is resistant?
a. mean
b. median
c. IQR
d. standard deviation
b. median
In a study of memory recall, 10 students from a large psychology class were selected at random and given 10 minutes to memorize 20 nonsense words. Each was asked to list as many of the words as they could remember both 1 hour and 24 hours later. Use the following data to determine whether the number of words recalled 1 hour after memorization exceeds the number of words recalled 24 hours later by more than 3.
In baseball, a perfect game is when a pitcher does not allow any hitters to reach base in all nine innings. Historically, pitchers throw a perfect inning (an inning where no hitters reach base) about 40% of the time. To throw a perfect game, a pitcher needs to have nine perfect innings in a row. Assuming a pitcher's performance in each inning is independent of his performance in other innings, what is the probability that a pitcher has a perfect game?
0.0002621
A company claims to have developed a new AAA batter that lasts longer than its regular AAA batteries. Based on years of experience, the company knows that it's regular AAA batteries last for 30 hours of continuous use. An SRS of 15 new batteries lasted an average of 33.9 hours with a standard deviation of 9.8 hours. What is the test statistic?
1.5413
What is the Law of Large Numbers?
The proportion of times that a particular outcome occurs in many repetitions will approach a single number.
What is the formula for outliers?
Q1-1.5IQR and Q3+1.5IQR
How do you increase power?
Increase alpha or increase sample size (n)
The First Trimester Screen is a noninvasive test given during the first trimester of pregnancy to determine if there are specific chromosomal abnormalities in the fetus. According to the study published in the New England Journal of Medicine, approximately 5% of normal pregnancies will receive a positive result Among 100 women with normal pregnancies, what is the probability that at least one will be a false positive?
0.9441
In a study of 3000 randomly selected teens in 1988, 15% showed some hearing loss. In a similar study of 1800 teens in 2005, 19.5% showed some hearing loss. What is the test statistic?
-4.04798
Define point estimator
What is the empirical rule?
68-95-99.7
Check conditions for the following scenario:
Snake experts believe venomous snakes inject different amounts of venom when killing their prey. Researchers at the University of Wyoming studied this and reported their results in "Venom Metering by Juvenile Prairie Rattlesnakes, Crotauls v. Effects of Prey Size and Experience." The researchers measured the average amount of venom used to kill a small mouse for 21 randomly selected inexperienced hunting snakes. Then, they measured the amount of venom used to kill a small mouse for a random sample of 21 experienced hunting snakes.
We are given random samples.
There are more than 210 experienced hunting snakes and more than 210 inexperienced hunting snakes.
The sample sizes of 21 are suitable to assume the normal condition as long as the data is not skewed or have any particular outliers.
The Kaiser Family Foundation released a study about the influence of media in the lives of young people aged 8-18. In the study, 17% of the youth were classified as light media users, 62% were classified as moderate media users, and 21% were classified as heavy media users. Of the light users who responded, 74% described their grades as good while only 68% of the moderate users and 52% of the heavy users described their grades as good. What percent of youth with good grades are heavy users of media?
16.63%.
What test would you use for the following scenario:
A study followed a random sample of 8474 people with normal blood pressure for four years. All the individuals were free of heart disease at the beginning of the study. each person took the Speilberger Trait Anger Scale test, which measures how prone a person is to sudden anger. Researchers also recorded whether each individual developed coronary heart disease (CHD). This includes people who had heart attacks and those who needed medical treatment for heart disease. *insert data* Does the data give convincing evidence that there is a link between anger and heart disease?
chi-square test of association.
What is power (beta)?
The probability that you reject H0 when HA is true.