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I/O Psych 542
Exam 1 Part 2
| Question | Answer |
|---|---|
| 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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