null hypothesis

(NH; symbol: H₀) a statement that a study will find no meaningful differences between the groups or conditions under investigation, such that there is no relationship among the variables of interest and that any variation in observed data is the result of chance or random processes. For example, if a researcher is investigating a new technique to improve the skills of children who have difficulty reading, the null hypothesis would predict no difference between the average reading performances of those children who receive the intervention and those who do not. The NH is contrasted with the alternative hypothesis, which is a prediction of a significant finding (e.g., a significant difference between sample means, a correlation that is significantly different from zero). Statistical procedures are applied to research data in an attempt to disprove or reject the NH at a predetermined significance level. See hypothesis testing.

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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.