Descriptive statistics
Statistics that describe a set of data
Histogram
A visual representation of the distribution of quantitative data (bar graph)
Measure of central tendency
Attempt to mark the center of a distribution
What are the three most common measures of central tendency?
Mean, median, mode
Mean
Average of the total of all scores in a distribution
Median
Central score of a distribution
Mode
Score that appears the most frequently
Skewed distribution
An unsymmetrical distribution skewed by outliers
Positive skew
More low cores than high scores, mean is higher than median
Negative skew
More high scores than low scores, median is higher than mean
Bimodial distribution
Distribution in which two scores appear equally frequently and more frequently than any other score
Measures of variation/variability
Descriptive statistical measures that show the diversity of a distribution
Range
Distance between the highest and lowest score
Variance
Average of each point from the mean
Standard deviation
Measures the square root of the variance
What are three measures of variation/variability?
Range, variance, standard deviation
Normal curve
A theoretical bell-shaped curve for which the area under the curve lying between any two z-scores has been predetermined
Z-scores
Measure the distance of a score from the mean in units of standard deviation
Percentiles
Indicate the distance of a score from 0
Inferential statistics
Statistics that determine whether findings can be applied to the larger population from which the sample was selected
Sampling error
The extent to which a sample differs from the population
P-value
Gives the probability that the difference between groups is due to chance
The _______ the p-value, the more _________ the results
Smaller, significant
What is the cutoff for statistically significant results in terms of p-values?
.05 (5% chance the results occurred by chance)
