Symbols
What is this symbol used for α?
significance level
What does a correlation coefficient (r) measure?
The strength and direction of a linear relationship between two quantitative variables
Nationwide 13.7% of employed wage and salary workers are union members. A random sample of 300 local wage and salary workers showed that 50 belong to a union. At a 10% significance level, is there enough convincing evidence to conclude that the proportion is different from 13.7%?
one-sample z test for population proportion
What is the probability of flipping heads on a fair coin?
0.5 or 50%
What does the acronym SOCS stand for?
Shape, Outliers, Center, Spread
What is this symbol used for μ?
population mean
What values of r indicate a strong correlation?
Values closer to -1 or 1
Usually r>0.7
An association of Christmas tree growers sponsored a sample survey of 500 randomly selected households to help improve the marketing of Christmas trees. The tree growers want to know if there is a difference in preference for natural trees vs artificial trees between urban and rural households. Among the 160 who lived in rural areas, 64 had a natural tree. Among the 261 who lived in an urban area, 89 had a natural tree.
two sample z interval for p1-p2
What is the general addition rule for probability?
P(A or B) = P(A)+P(B)-P(A and B)
What is the difference between mean and median?
Mean is the average of the data while the median is the direct middle value when the data is ordered. The median is less affected by outliers.
What is this symbol used for σ?
population standard deviation
What type of model results when both x and y values are transformed using logarithms?
A power model
Is gender a factor in a person's favorite fruit? 400 men and 500 women were asked their favorite fruit to see if the distribution of favorite fruit is the same for men and women?
chi-squared test for homogeneity
What are independent events?
Two events are independent if the occurrences of one does not affect the probability of the other
What type of graph is best for displaying the distribution of one quantitative variable?
Histogram or boxplot
What is this symbol used for χ2?
chi-squared
How can you tell if a linear model is a good fit for your data using a residual plot?
If the residual plot shows similar scatter around "residual=0" for all x
A high-school administrator is concerned about the amount of sleep the students in his district are getting selects a random sample of 14 seniors in his district and asks them how many hours of sleep they get on a typical school night. He then uses school records to determine the most recent grade-point average (GPA) for each student
linear regression t test for slope β
A die is rolled, what is the probability of rolling an even number?
(2,4,6)
3/6
0.5
What does Standard Deviation measure?
The average distance of the data values from the mean. It tells how spread out the data is
What is this symbol used for σ²?
population variance
What is a residual in a regression model?
A residual is the difference between the actual value and the predicted value
Do people who wear hats spend more money at the mall than people who do not wear hats? 300 people wearing hats and 300 people not wearing hats were followed asked how much money they spent at the mall.
Two-sample t test for μ1-μ2
What is the difference between joint probability and conditional probability?
Joint- the probability of two events occurring together P(A and B)
Conditional- the probability of one event given that another one has occured P(A|B)
Mean- outliers can significantly change the mean by pulling it towards the outlier
Median- more resistant to outliers and will remain relatively unchanged