Stats

How are independent and dependent variables related?

Independent variables are like a treatment or intervention while the dependent variable typically represents the outcome of the I.V

What are the three types of variability that can be used to describe spread or dispersion?

Range, interquartile range, and standard deviation are the three commonly used measures of dispersion.

What does it mean that correlation does NOT equal causation? What are alternative explanations for correlations other than causation?

Just because two things may be related, that does not mean one thing causes the other. Correlations express the association that exists between two variables, so they have nothing to do with causality (p. 95)

What are the measures of central tendency?

A measure of central tendency is a single value that attempts to describe a set of data by identifying the central position within that set of data. Ex: Mean, Mode, and Median

How do you calculate the mode of a distribution?

A number that appears most often is the mode.What if there happens to be two modes? If a set has two modes, then both of those numbers are considered to be modes of the set. When this happens, the set is called bimodal.

How is the strength of the correlation determined?

By the absolute value (negatives don't matter; so -0.5 is stronger than .2 correlation because 0.5 is farther away from zero than 0.2)

What's the difference between the coefficient of determination and the coefficient of alienation?

Coefficient of determination (r2)- the percentage of variance in one variable that is accounted for by the variance in the other variable Coefficient of alienation (1 - r2)- the amount of unexplained variance; the amount of variance in Y not explained by X (and vice versa)

What are the differences between continuous and discrete variables? What types of correlations go along with each?

Continuous-Fall on a continuum Age, height, test score, income Pearson's product-moment correlations Rxy = the correlation between variables x and y Discrete- Has distinguishable spaces b/w values # of dogs, people (can be counted)

What is the purpose of a correlation matrix, and why are the diagonal pairs all equal to 1.0?

Correlation matrices allow you to see correlations for more than two variables Variables compared with themselves are perfectly correlated (the matrix creates a mirror image of itself, p. 91)

What is the difference between descriptive and inferential statistics?

Descriptive statistics uses the data to provide descriptions of the population, either through numerical calculations or graphs or tables. Inferential statistics makes inferences and predictions about a population based on a sample of data taken from the population in question.

What is the difference between the mean and the median?

Mean: the average of the numbers, Median: middle number when they lined up from the greatest to the least.

How do you calculate the median?

Middle lined from the greatest to the least

When would median be a better measure of central tendency?

The median is usually preferred to other measures of central tendency when your data set is skewed (i.e., forms a skewed distribution) or you are dealing with ordinal data.

When would mode be a better measure of central tendency?

The mode can only be used when dealing with nominal data. For this reason, the mode will be the best measure of central tendency (as it is the only one appropriate to use) when dealing with nominal data.

What are the different types of reliability and validity? What is the difference between the two?

Validity makes sure the test measures what it's supposed to while reliability ensures that it is consistent in measuring what it is designed to measure (whether a test measures something consistently p. 111)

Why are the measurement concepts of reliability and validity important to the research process?

They ensure your results (of experiment etc.) are not in question, that they're accurate

How might squaring a correlation coefficient be useful to understanding the relationship between two variables?

To determine exactly how much of the variance in one variable can be accounted for by the variance in another variable

What is the formula for computing the mean?

add up all the numbers, then divide by how many numbers there are. In other words it is the sum divided by the count.

What do scatterplots show?

correlations

What is the difference between exclusive range and inclusive range?

inclusive means within and the number n , while exclusive means within and without the number n