Unit 1+2
Which of the following values of r is strong and positive?
-0.99, 0.56, 0.12, 0.95, -0.43
0.95
Does a cluster random sample produce heterogeneous or homogeneous groups?
Heterogeneous groups because you take a mini population
What does it mean for events to be mutually exclusive?
Two events are disjoint (mutually exclusive) if they share no outcomes in common. If A and B are disjoint, then knowing that A occurs tells us that B cannot occur. the probability for events A and B occurring is 0
What is the z* for a 95% confidence level
1.960
What is an explanatory variable?
What is a response variable?
Explanatory: Variable that helps explain/predict or influences changes in a response variable. Assigned to the x-axis.
Response:A variable that measures an outcome of a study. The variable you are hoping to predict or explain. Assigned to the y-axis
Identify the type of sampling method used:
A teacher is investigating how many students in their school play a fall sport. The teacher surveys the first 100 students that arrive at school one morning. On average, 46 of the students did a fall sport.
Convenience sampling.
What are the conditions for independence/normal distribution and how do you check them?
Independence-
10%: Sample must be less than 10% of total population n10<N
Random Sampling: Needs to be a randomly selected sample or random assignment
Approx. Normal-
Large counts: np>10 & n(1-p)>10
What are the number of sample(s) and variable(s) in each chi squared t test?
-Chi Square t-Test for Independence: 1 sample and 2 variables
-Chi Square t-Test for Homogeneity: 2 samples and 1 variable
-Chi Square t-Test for Goodness of Fit: 1 sample and 1 variable
How do you interpret r2
r2 percent of the variation in the response variable is explained by the linear relationship with explanatory variable.
Explain undercoverage, response bias, and nonresponse bias
Undercoverage: when some members of a population cannot or are less likely to be included in a sample
Nonrepsonse: when someone is in the sample but chooses to not respond
Response: when the sample is inaccurate or not honest in response
What is the interpretation of expected value?
If many, many (units) are randomly selected, the average number of (x-variable) is about (mean).
What plots go with which condition during a Linear Regression t interval or test for slope?
Linear: scatterplot and residual plot
Independent: No plots- condition refers to if sample is random and 10% condition
Approx. Normal: Dotplot of Residuals
Equal SD: Residual plot
What is the relationship between the mean and median on the following distributions: unimodal and symmetric, unimodal and skewed left, and unimodal and skewed right.
-Unimodal and symmetric the mean and median are about the same.
-Unimodal and skewed left the mean is less than the median.
-Unimodal and skewed right the mean is greater than the median.
Identify the type of bias and direction of bias: A manager is threatening to fire his employees if they are late to their shift more than 7 times. He asks 120 of his employees if they have been late to work more than 7 times this year. Only 13 of the employees responded that they have been late more than 7 times.
Response bias and underestimate.
What are the conditions for a binomial distribution and what are the conditions for a geometric distribution?
Binomial: Binary, Independent, Number of Trials, Same Probability
Geometric: Binary, Independent, Number of Trials UNTIL Success, Same Probability
What is the correct inference procedure? Have clothing preferences and styles changed between last month and this month? 500 people were observed last month and this month to see what brand of clothing they were wearing.
Chi Square t-Test for Goodness of Fit
Name one advantage of the following graphs: dotplot, stemplot, histogram.
Dotplot: Advantages- Can see all data values, and order from least to greatest. .
Stemplot: Advantages- Can see all data values, and ordered from least to greatest.
Histogram: Advantages- summary of data distribution, and good for large data sets.
Describe how to get a sample of 10 students out of a population of 100 students using SRS
Number all the students 1-100
-using a random number generator, generate 10 unique integers from 1-100, inclusive.
-find the students with the corresponding integers and survey them.
A soccer player makes 73% of her penalty kicks. We ask her to kick free throws until she misses. Let X= number of penalty throws the player kicks until she misses.
-What is the inequality to solve for the probability the player will make 6 shots before she misses?
Geometric, p=0.27
x=# of shots until she misses
-p(X=7)= (.73)^6(0.27)^1
If a researcher changes the significance level from 0.05 to 0.01 and all the factors stay the same (sample size, population standard deviation, and true population mean), what is the impact of this change on power and probability of Type ll error?
Power decreases and probability of Type ll error increases.