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Psych Stats Midterm
Nominal Data - Data which consists of names, labels, or categories. ordinal data - a type of data that refers solely to a ranking of some kind z score formula - z = (x - μ)/σ standard deviation - the square root of the variance IQR (interquartile range) - measure of statistical dispersion, being equal to the difference between the upper and lower quartiles, IQR = Q3 − Q1. Mean symbol for population - μ Mean symbol for sample - m Variance symbol (population) - σ Variance symbol (sample) -
S
standard deviation symbol for sample - S^ standard deviation symbol for population - σ^ z table - A table containing a list of z scores and the area of the curve that is between the distribution mean and each individual z score. Null Hypothesis (H0) - the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error. Alternate Hypothesis (H1) - A statistical hypothesis that offers an alternative to the null hypothesis when the null is rejected. negatively skewed - a distribution that trails off to the left positively skewed - a distribution that trails off to the right quasi-experiment - An experiment in which investigators make use of control and experimental groups that already exist in the world at large. Also called a mixed design. frequency distribution -
self-selection bias - A bias that occurs because people who feel strongly about a subject are more likely to respond to survey questions than people who feel indifferent about it. sampling error - an error that occurs when a sample somehow does not represent the target population sampling distribution - the distribution of values taken by the statistic in all possible samples of the same size from the same population Central Limit Theorem - The theory that, as sample size increases, the distribution of sample means of size n, randomly selected, approaches a normal distribution. standard error of the mean - the standard deviation of a sampling distribution confidence interval - the range of values within which a population parameter is estimated to lie Type I error (alpha) - False positive results ex: reject the null hypothesis when you should accept it Type II error - false negative statistical power -
the likelihood of finding a statistically significant difference when a true difference exists mean formula - Σx/n Variance formula - ∑(x - X)²/n- Variance - subtract the mean from each value and square that. add all of those values together and divide by number of data points-1. ex. {3,5,8,1) mean: (3+5+8+1)/4=4. variance: ( (3-4.25)^2 + (5-4.25)^2 + (8-4.25)^2 + (1-4.25)^2 )/4- confidence interval - CI confidence interval formula - mean +- z*SE
- for a 95% CI, z will be 1. (z could also be t) standard error of the mean formula - standard error = population standard deviation divided by the square root of sample size σM= σ/sqrt{ M }
