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Two-Proportion z-TestStatLens

Choose a dataset:

Paste data (CSV with group and outcome columns):

Open a CSV, TSV, or JSON file:

Group 1 Group label: Successes: Sample size (n₁):

Group 2 Group label: Successes: Sample size (n₂):

Results update as you type — no need to press anything.

Grouping variable: Outcome variable:

Count as success:

Parameters

H₀: p₁ − p₂ = 0 =

H_a: p₁ − p₂ 0 0

Select a dataset or enter summary statistics — results appear automatically.

Just estimating? Confidence Interval for a Difference in Proportions →

Two-Proportion z-Test

Compare the proportions of two independent groups (p₁ − p₂), using a z-statistic and the standard normal distribution.

Load data from the Datasets, Edit Data (a group column and an outcome column), or Open File/URL tab, or use Enter Summary to type the successes and n for each group.
Grouping / outcome selectors and Count as success let you choose the columns and the success category when loading raw data. Swap Group 1 ↔ Group 2 flips which group is subtracted.
Alternative (H_a): click the toggle to cycle ≠, <, > for a two-sided or one-sided test.
Null value: standard mode tests p₁ − p₂ = 0. Turn on Expert mode (settings gear) to make the null difference editable.
Conditions checkpoint reminds you to check the success/failure counts in each group.
Results — the z-statistic, p-value, confidence interval, and plot — appear automatically as you change inputs. There is no Compute button.

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