significance level

(symbol: α) in significance testing, a fixed probability of rejecting the null hypothesis of no effect when it is in fact true. It is set at some value, usually .001, .01, or .05, depending on the consequences associated with making a Type I error. When a particular effect is obtained experimentally, the probability level (p) associated with this effect is compared to the significance level. If the p value is less than the α level, the null hypothesis is rejected. Small p values suggest that obtaining a statistic as extreme as the one obtained is rare and thus the null hypothesis is unlikely to be true. The smaller the α level, the more convincing is the rejection of the null hypothesis. Also called alpha level.

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Psychology term of the day

December 18th 2024

sampling

n. the process of selecting for study a limited number of units from a larger set. The term most often refers to the selection of respondents, observations, or cases for inclusion in experiments, surveys, interviews, or other research. However, sampling can also involve selecting theoretical constructs to study, selecting measurement instruments from a broad set of potential options, or selecting time points at which to observe individuals or cases. There are various different selection methods, including simple random sampling, stratified sampling, convenience sampling, and quota sampling. Each approach has a different potential of obtaining a sample appropriately representative of the population under study.