Distributions
what do we call a perfectly symmetrical, bell shaped distribution?
Normal distribution
what measure of central tendency is the most frequent value?
Mode
which hypothesis states that there is no effect of difference?
null hypothesis
which test do you use when you have the population SD?
Z-test
A professor wants to know if her class’s average test score is different from the known national average of 75, but the population standard deviation is unknown. What test should she use?
One-sample t-test
what is the effect size measure called?
Cohen's d
what do we call a distribution that has two peaks?
bimodal distribution
what is the arithmetic average?
Mean
which hypothesis predicts a real effect or difference?
alternative hypothesis
which test compares a sample mean to a known population mean when the population SD is unknown?
one sample t-test
A researcher measures participants’ heart rates before drinking caffeine and again after drinking caffeine. What test should they use?
Paired samples t-test
what does a Cohen's d of .2 indicate?
small effect
what do we call a distribution with a long right tail?
positively skewed distribution
what measure splits the data set in half?
Median
what value tells you the probability of your results if the null is true?
p-value
which test compares the means of two independent groups?
independent samples t-test
A psychologist wants to compare stress levels between students who meditate and students who do not meditate. These are two different groups of people. What test should be used?
Independent-samples t-test
What does a Cohen’s d of 0.5 indicate?
Medium effect
in what distribution is the mean smaller than the median and mode?
negatively skewed distribution
what statistic represents the average distance of scores from the mean?
standard deviation
what error occurs when you fail to reject a false null hypothesis?
which test compares two related or matched sets of scores?
paired samples t-test
A researcher wants to test whether a sample’s average reaction time differs from a population value. The population mean is 1.2 seconds, and the population standard deviation is .2 seconds. What test should they use?
Z-test
What does a Cohen’s d of 0.8 or greater indicate?
large effect
what type of distributions has mostly low values and only a few high ones?
positively skewed distribution
what is the square of the standard deviation?
variance
what is the probability of correctly rejecting a false null?
statistical power
what statistic combines the standard deviations from two groups for an independent t-test?
pooled SD
A scientist compares the problem-solving scores of two groups, and the groups have unequal sample sizes (e.g., n = 20 vs. n = 35). What test should they use?
Independent-samples t-test
what graph uses bins to show frequencies of values?
histogram
what statistic represents the average variability of sample means from the population mean?
standard error
what type of error occurs when you incorrectly reject the null that is actually true?
type I error
Which table provides critical values for hypothesis testing when population SD is unknown?
T-table
A teacher wants to examine whether students’ memory scores change after a training session by comparing each student’s before and after scores. What test should be used?
Paired-samples t-test