Updated 1 Exam stats in psych made by me

What is a variable?

Something that can change or have different values. Example: age, height, test score.

What is an independent variable?

The variable you manipulate; what you are interested in.

What is a dependent variable?

The variable you measure to see if it changes.

What is a frequency distribution?

A list or table that shows how often each value occurs.

What is a grouped frequency distribution?

A frequency distribution that puts values into groups or ranges.

What is a population?

Everyone or everything you want to study. Also called the universe.

What is a sample?

A smaller group taken from the population.

What is a sample statistic?

A number that describes a sample.

What is a descriptive statistic?

A number that describes data.

What is an inferential statistic?

A statistic used to make conclusions about a larger population.

What is a population parameter?

A number that describes a population.

What is a theory?

A general explanation for something.

What is a hypothesis?

A prediction that can be tested.

What does random selection mean?

Choosing people from a population by chance.

What does random assignment mean?

Putting people into groups by chance.

What does empirical mean?

Based on observations or data; can be meausred

What is correlation?

A relationship between two variables.

What is positive correlation?

When one variable goes up, the other tends to go up too.

What is negative correlation?

When one variable goes up, the other tends to go down.

What are the four levels of measurement?

Nominal, ordinal, interval, and ratio.

What is nominal measurement?

Categories with no order. Example: eye color.

What is ordinal measurement?

Categories that have an order. Example: 1st, 2nd, 3rd place.

What is interval measurement?

Numbers with equal spaces between them, but no true zero. Example: temperature in Fahrenheit.

What is ratio measurement?

Numbers with equal spaces and a true zero. Example: height or weight.

What does mutually exclusive mean?

A person or item can only fit into one category.

What does collectively exhaustive mean?

There is a category for every possible answer.

What are descriptive statistics used for?

To describe and summarize data.

What are inferential statistics used for?

To use a sample to learn about a population.

What are the four types of studies?

Observational, correlational, quasi-experiment, and experiment.

What is an observational study?

You observe people without changing anything.

What is a case study?

A detailed study of one person, group, or case.

What is a survey?

A study where people answer questions.

What is naturalistic observation?

Watching behavior in its normal setting.

What is a correlational study?

A study that looks at the relationship between variables.

What is a quasi-experiment?

A study that is like an experiment but does not have full experimental control.

What is an experiment?

A study where the researcher changes one variable and measures the effect.

What are the three goals of science?

Describe, predict, and explain.

What does describe mean?

To tell what is happening.

What does predict mean?

To tell what you expect to happen.

What does explain mean?

To understand why something happens.

What is central tendency?

A way to describe the center of a group of scores.

What are the three measures of central tendency?

Mean, median, and mode.

What is the mean?

The average of the scores.

What is the median?

The middle score when scores are put in order.

What is the mode?

The score that occurs most often.

What is the range?

The distance between the highest and lowest scores.

What is a deviation from the mean?

How far a score is from the mean.

What is mean deviation?

The average distance scores are from the mean.

What is variance?

A measure of how spread out the scores are.

What is standard deviation?

A measure of how spread out scores are from the mean.

What happens to standard deviation when scores are very spread out?

The standard deviation gets larger.

What happens when scores are close together?

The standard deviation gets smaller.

What is a standard score or Z score?

A score that tells you how far a score is from the mean in standard deviation units.

What does a positive Z score mean?

The score is above the mean.

What does a negative Z score mean?

The score is below the mean.

What does a Z score of 0 mean?

The score is at the mean.

What is an outlier?

A score that is very different from the other scores.

Which measure of central tendency is most affected by outliers?

The mean.

Which measure is less affected by outliers?

The median.

What is a problem with the range?

It only uses the highest and lowest scores.

What is a symmetrical distribution?

A distribution that looks the same on both sides.

What is a skewed distribution?

A distribution that is not symmetrical.

What is positive skew?

A distribution with a long tail to the right.

What is negative skew?

A distribution with a long tail to the left.

What happens to the mean, median, and mode with positive skew?

The mean is usually highest, then the median, then the mode.

What happens to the mean, median, and mode with negative skew?

The mean is usually lowest, then the median, then the mode.

What is a normal distribution?

A symmetrical, bell-shaped distribution.

What are the mean, median, and mode in a normal distribution?

They are all at the center.

What is the normal curve?

A bell-shaped curve that shows a normal distribution.

What happens to the normal curve when standard deviation is larger?

It becomes wider and flatter.

What happens when standard deviation is smaller?

It becomes narrower and taller.

What is the 68-95-99.7 rule?

About 68% of scores are within 1 SD, 95% within 2 SDs, and over 99% within 3 SDs of the mean.

What is a probability distribution?

A distribution that shows how likely different values or outcomes are.

How is a normal distribution related to probability?

The area under the normal curve represents probability.

What is percentile rank?

The percentage of scores that are at or below a certain score.

What does being at the 90th percentile mean?

You scored higher than about 90% of the group.

What is a bar graph?

A graph that uses bars to show data for different categories.

What is the difference between a bar graph and a frequency distribution?

A frequency distribution shows how often values occur; a bar graph displays that information visually.

What is a histogram?

A graph that uses connected bars to show numerical data.

What is a pie chart?

A circle divided into sections to show parts of a whole.

What is a box plot?

A graph that shows the center and spread of a set of data.

What is a scatterplot?

A graph that shows the relationship between two variables.

What is a dot plot?

A graph that uses dots to show individual data values.

Sample symbol

n

Population mean symbol

μ

Sample variance

s²

Population variance

σ²