BackTwo Means - Unknown, Equal Variance definitions
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1/15BackSkip to main contentBackPooled Standard Deviation
A weighted average of two sample variances, used to estimate a common population standard deviation when variances are assumed equal. Equal Variance Assumption
The premise that two populations have the same variance, allowing for more precise statistical testing using pooled data. Hypothesis Test
A structured process for deciding if sample data provides enough evidence to support a specific claim about population parameters. Null Hypothesis
A statement asserting no difference or effect, typically that two population means are equal. Alternative Hypothesis
A claim suggesting a difference or effect exists, such as one mean being greater than the other. Test Statistic
A calculated value, often a t-score, used to determine how far sample results deviate from the null hypothesis. P-value
The probability of observing results as extreme as those in the sample, assuming the null hypothesis is true. Alpha Level
A threshold probability, often 0.05, used to decide whether to reject the null hypothesis. Degrees of Freedom
A value based on sample sizes, used to select the correct distribution for hypothesis testing. Independent Samples
Groups selected so that the outcome of one does not influence the outcome of the other. Sample Mean
The average value calculated from a group, representing the central tendency of the sample. Sample Standard Deviation
A measure of variability within a sample, indicating how spread out the data points are. T-table
A reference chart used to find probabilities and critical values for t-distributions based on degrees of freedom. Normal Approximation
An approach where large sample sizes allow the use of normal distribution properties for inference. A/B Test
A comparison of two groups to determine if a change or treatment leads to a statistically significant difference.
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