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I/O Psych 542

Exam 1 Part 2

QuestionAnswer
random sample one in which every member of the population has an equal chance of being selected into the study
convenience sample one that uses participants that are readily available
cluster sample a sampling technique where the entire population is divided into clusters and a random sample of these clusters are selected. All observations in the selected clusters are included
stratified sample taking samples from each stratum or sub-group of a population. When we sample a population w/ several strata, we generally require that the proportion of each stratum in the same be the same as in the population
volunteer sample a special kind of convenience sample in which participants actively choose to participate in a study (they self-select themselves, which is why it’s also known as a self-selected sample)
randomized block sample blocking is the arranging of experimental units in groups (blocks) that are similar to each other (example: sex).
replication the duplication of scientific results, ideally in a different context or with a sample that has different characteristics
subjective probability the likelihood that a certain outcome will occur out of all possible outcomes
Expected Relative-Frequency Probability the likelihood of an event occurring based on the actual outcome of many, many trials
trial each occasion that a given procedure is carried out
outcome results of a trial
control group a level of the independent variable that does not receive the treatment of interest in a study
experimental group a level of the independent variable that receives the treatment or intervention of interest
floor effect a situation in which a constraint prevents a variable from taking on values below a certain point
ceiling effect a constraint prevents a variable from taking on values above a given #. Ex: on an easy quiz a # of students would be 100, w/some at the lower end. Some students w/high scores may have scored above 100 w/ extra credit, but were limited to a ceiling of 100
null hypothesis a statement that postulates that there is no difference between populations or that the difference is in a direction opposite from that anticipated by the researcher
research hypothesis a statement that postulates that there is a difference between populations, or sometimes, more specifically, that there is a difference in a certain direction, positive or negative (also known as the alternative hypothesis)
type 1 error when we reject the null hypothesis but the null hypothesis is correct
type 2 error when we fail to reject the null hypothesis, but the null hypothesis is false
Type I Errors lead to action, at least until we discover the error. A false-positive pregnancy test may tell fly. & buy baby clothes.Or a person mistakenly diagnosed w/a severe illness may start treatment. Researchers consider Type I Error to be detrimental because people take action on a mistaken finding.
Type II Error is a false-negative results in a failure to take action. A pregnant woman who received a false-negative may continue to drink and smoke, which could harm the baby. Or a truly effective Alzheimer’s drug may be kept off the market, those w/the disease will continue to suffer
normal curve a bell-shaped curve that is unimodal, symmetric & defined mathematically. based on Abraham De Moivre’s mathematical equation that he believed could predict random events. The actual curves were later drawn by Daniel Bernoulli & Augustus De Morgan
standardization converts individual scores to standard scores for which we know the percentiles. converts indv. scores from diff. normal distr. to a shared normal distr. with a known mean, stdv & percentiles. done to make meaningful comparisons.
standard normal distribution a normal distribution of z scores. (Note: z scores – a normal distribution of standardized scores)
central limit theorem this asserts that a distribution of sample means approaches a normal curve as sample size increases
central limit theorem demonstrates two important principals: • Repeated sampling of means approximates a normal curve, even when the original population is not normally distributed • A distribution of means is less variable than a distribution of individual scores
standard error the name for the standard deviation of a distribution of means
confidence intervals an interval estimate, based on the sample statistic, that includes the population mean a certain percentage of the time, were we to sample from the same population repeatedly.
point estimate a summary statistic from a sample that is just one number used as an estimate of the population parameter
variance the average of the squared deviations from the mean. Variance refers to variability (variability – a numerical way of describing how much spread there is in a distribution)
standard deviation the square root of the average of the squared deviations from the mean, and is the typical amount that each score varies, or deviates, from the mean
Created by: cjd021
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