Sampling Solves
This type of sample accurately reflects the population it came from
Representative sample
What term is used to describe the probability level a researcher sets before running a test, and serves as a defining point on the null distribution?
Alpha
This symbol is used to represent the y-intercept of a regression line
a
Y'=bx+a
Lena runs her analysis the old school way. Her observed value is 3.2 and the critical value for her chosen alpha is 3.84. She announces that her results are statistically significant.
The observed value is less than the critical value, so she should retain Ho
A correlation of -0.8 is stronger than a correlation of 0.6
True
Both 1 and -1 imply perfect correlation
A researcher takes a sample of 100 Psychology students at UVU. What would the population they are representing with this sample.
UVU psychology students only
When the p is ____ reject the ____
When p value is lower than the alpha
A regression line has a high y-intercept and continues in a downward slope to the left. Whats a possible b value
Anything negative
Lola wants to know whether the number of males and females in her sample matches what she’d expect in the population. She runs a two-way chi-square.
One variable so she should use a one-way Chi-squared
A perfect correlation (r) of 1 or -1 means one variables change must cause the other variable to change as well
False
Correlation does not imply causation
Jackson wants to test if basketball players score more points depending on how tall they are. He decides to take his teammates measurements and track how many times they score over the course of a season. What type of sample is this.
A Convenience Sample
The one way Chi-squared test states there is no statistically significant _____ while the two-way Chi-squared test would use the term ______.
One-way: Difference
Two-way: Association
What is the slope of the regression line is Y'=10, X=2, and a=-4
slope (b)=7
Marcus is a resident assistant who wants to predict a student’s GPA from the number of nights per week they go out. He gathers data from 40 students, checks the scatterplot (the pattern is linear), and enters everything into JASP with GPA as the dependent variable and nights out as the covariate. The coefficients table gives him the equation Y’ = -0.2X + 3.8. He writes in his report, “As the number of nights out increases, predicted GPA also increases.” What is his mistake?
The slope is negative (-0.2), so as nights out increase, predicted GPA decreases
Regression can only be used on linear relationships. It won't work on a non-linear scatterplot.
True
A researcher randomly selects 100 students for a survey, but only the most satisfied students send their surveys back. Is the problem sampling error or sampling bias, and why?
Sampling bias. The final sample is no longer representative because of who chose to respond, even though the original selection was random.
The one-way chi-square is also called the ______ of ______ test.
Goodness of fit
0
Samuel wants to study the correlation between apples eaten and weight gained. He decides to run a correlation study with an alpha of .05 and critical value of 3.21. After doing his calculations he gets a p-value of .012 and a observed value of 3.12. Because both values are lower than their counterparts he decides to reject the null hypothesis.
His calculations must be wrong as a p-value less than the alpha, would also have a observed value thats GREATER than the critical value.
In a two-way Chi-squared test, both variables should be quantitative
Both variables should be categorical for a two-way chi-squared test
Alyssa says that that a sample of 30 from a skewed population indicates that a larger sample size would lead to an even greater skew. What theorem would argue against that?
Central Limit Theorem:
As sample size increases, the distribution will become closer to a normal curve
What term is used to describe the standard deviation of the sampling distribution of the means, which can be calculated by dividing the population standard deviation by the square root of the sample size?
Standard error of the means (SEM)
This is also in support of the central limit theorem
Name the three assumptions of linear regression
1. A linear relationship exists
2. the residuals are independent of one another
3. homoscedasticity. Homoscedasticity means the residual points are about the same distance from the regression line across the scatterplot.
Dana is a psychology student studying whether hours of sleep are related to GPA in college students. For Step 1, she writes, “Ho: There is no statistically significant relationship between hours of sleep and GPA.” She decides on an alpha of .05 and mails her survey to every student enrolled in her 8 a.m. Intro to Psychology section. Of the 120 students who respond, she records average nightly hours of sleep and current GPA. She gets r = .32 with p < .027. She rejects the Ho, squares r to find an effect size of about 10%, and writes that sleep is correlated to GPA in college students
Sampling bias
She sampled her early morning class and applied it to all college students when thats not her population
The mean of a sampling distribution of means is equal to the population mean
The mean of means can be written as Mu the population mean