Central Tendency & Variability
This measure of central tendency is the arithmetic average of a set of scores.
What is the mean?
A distribution that is perfectly symmetrical and bell-shaped is called this.
What is a normal distribution (or curve)?
This is the hypothesis that states there is no effect or no difference in the population.
What is the null hypothesis?
This level of measurement has equal intervals and a true zero point that means complete absence of the variable. (reaction time, number of errors on a test)
What is ratio?
In an experiment, the variable that the researcher deliberately manipulates or changes.
What is the independent variable?
This measure of central tendency is simply the most frequently occurring score in a set of data.
What is the mode?
This standardized score tells you how many standard deviations a raw score is from the mean.
What is a z-score?
Rejecting the null hypothesis when it is actually true is this type of error.
What is type 1 error? (Alpha) (false positive)
This level of measurement uses categories or names only, with no inherent order (ex. gender, blood type, eye color)
What is nominal?
A psychologist wants to know if caffeine improves memory. Participants drink either regular coffee or decaf, then take a memory test. The score on the memory test is this type of variable.
What is the dependent variable?
This measure of variability is the square root of the variance.
What is the standard deviation?
A distribution with a long tail on the right side is said to be skewed in this direction.
What is positively (or right) skewed?
The probability of obtaining results as extreme as (or more extreme than) those observed, assuming the null hypothesis is true, is called this.
The p-value
This level of measurement allows ranking or ordering of scores. (ex. finishing place in a race)
What is ordinal?
A study examines whether the number of hours of sleep the night before predicts how well students perform on an exam. Exam performance is this type of variable.
What is the dependent variable?
When a distribution is skewed, this measure of central tendency is usually preferred over the mean because it is less affected by extreme scores.
What is the median?
According to the approximation rule, about this percentage of scores in a normal distribution fall within two standard deviations of the mean.
What is 96%?
Failing to reject a false null hypothesis is this type of error.
What is type 2 error? (Beta) (false negative)
This level of measurement has equal intervals between scores but no true zero point. (ex. standardized IQ test, GPA)
What is interval?
Researchers assign people to either a mindfulness meditation group or a control group and later measure their stress levels. The group assignment (meditation vs. control) is this type of variable.
What is the independent variable?
In a normal distribution, approximately this percentage of scores falls within one standard deviation of the mean?
What is 34%?
If a student scores at the 84th percentile on a normally distributed test, their approximate z-score is this.
What is +1?
This is the conventional alpha level most commonly used in psychology research.
What is .05 (or 5%)?
A researcher records the number of Tims each participant checks their phone during a 30-minute waiting period. This variable is measured at this level.
What is ratio?
In a study testing whether a new therapy reduces symptoms of anxiety, the severity of anxiety symptoms measured after treatment is this type of variable.
What is the dependent variable?