Section 3.2

Reporting Statistics in APA Style

Q: Do I italicize p and t in APA style?

Yes. The rule is simple once you see it: statistical symbols written with Latin letters are italicized, and those written with Greek letters are not. So t, F, r, p, M, SD, d, N, and R² are all italic, while α, β, χ², and η² stay upright, even when they sit right next to an italic Latin symbol (it's R² but η²). The operators and labels around them (the '=' sign, parentheses, 'df', units) are never italicized. Getting this one rule right fixes the most frequently flagged APA error there is.

Q: What is the difference between N and n?

Capital N is the whole sample; lowercase n is a piece of it. So a study of 120 people split into two conditions reports N = 120 once, then n = 60 per group when it describes them separately. Both are Latin, so both are italic, and both keep the distinction in every table heading and figure note as well. The place it matters most is chi-square, which carries the total inside its parentheses: χ²(1, N = 120) = 6.30. A lowercase n there would tell a reader you had tested only one cell. The related habit worth copying: whenever a subgroup analysis drops people, give its own n rather than letting the reader assume the full sample carried through.

Q: My department uses a different style guide. Do these rules still apply?

The typography is APA's and the substance is everyone's. Which letters go italic, whether a number keeps its leading zero, and where the degrees of freedom sit are conventions that other style guides set differently, so follow whichever one your department names. What no guide disagrees about is what has to be there: the test statistic, its degrees of freedom, an exact p-value rather than a threshold, an effect size, and an interval around the estimate. A reader cannot judge your result without those five, whatever the house style dresses them in. If your department publishes no guide at all, use APA and say so once in your methods, which is a defensible choice nobody marks down.

A results paragraph is a tiny, rigid language. APA 7 fixes exactly how a t-test, an ANOVA, a correlation, or a regression coefficient is written — which letters are italic, whether a number gets a leading zero, how a p-value is rounded. Once you know the handful of master patterns, reporting statistics stops being a source of red ink and becomes copy-and-fill. This lesson is those patterns, plus the four rules that catch 90% of the mistakes.

The master patterns

Every result follows a template: the statistic, its degrees of freedom in parentheses, the value, then the p-value and an effect size. Learn these five and you can report almost any analysis you'll run in a thesis:

Analysis	APA 7 form
t-test	t(58) = 3.72, p < .001, d = 0.96
One-way ANOVA	F(2, 87) = 5.42, p = .006, η² = .11
Chi-square	χ²(1, N = 120) = 6.30, p = .012, V = .23
Correlation	r(58) = .34, p = .008
Regression	b = 0.42, SE = 0.14, β = .29, t(96) = 3.00, p = .003; model R² = .18, F(3, 96) = 7.02, p < .001

Italics: Latin yes, Greek no

The single most-broken rule. A letter that stands for a statistic gets italicized when it's Latin, and stays upright when it's Greek:

Italic (Latin): t, F, r, p, M, SD, d, N, n, R², b, SE, t, z, U, V.
Upright (Greek): α, β, χ², η², ρ, ω. So it's R² (Latin, italic) but η² (Greek, upright); β for a standardized coefficient stays upright even though the b beside it is italic.

Subscripts and the operators don't get italicized either — the "df" label, the parentheses, the "=" sign, and units all stay in normal type.

Leading zeros and decimals

Drop the zero before the decimal point only for numbers that can't exceed 1 in absolute value — p-values, correlations, and proportions. Everything that can be bigger than 1 keeps its leading zero:

p = .03, r = .34, β = .29: no leading zero (bounded by 1).
t = 3.72, M = 28.4, d = 0.96: keep the zero (d can, and often does, exceed 1).

Report most statistics to two decimals; p-values to two or three. Match the precision to the number's usefulness — nobody needs t = 3.7241.

The p-value rules

Three habits keep p-values honest and APA-clean:

Report the exact value when you can: p = .023, not "p < .05". The exact number is more informative and lets a reader judge for themselves.
Floor tiny values at .001. Anything smaller is written p < .001 — you never claim more precision than that.
Never write p = .000. Software prints that when the value is too small to display, but a probability is never exactly zero. Translate it to p < .001.

Means live in parentheses. When you mention a group's average, give its spread right beside it: "the nap group (M = 28.4, SD = 4.1)". Report the descriptives before the test that compares them, so the reader sees the raw picture before the verdict.

Where the confidence interval goes

The five patterns above are the skeleton, and APA 7 asks for one more bone: an interval around the estimate wherever one can be computed. The p-value says whether you can rule out zero. The interval says which values are still on the table, which is usually the question your reader actually has. From Output to Results Section shows where it sits in the sentence; this is what it looks like.

The form is 95% CI [lower, upper]. Square brackets, the two limits separated by a comma, the confidence level in front. When every interval in your paper is a 95% one, say so the first time and then stop repeating it: 95% CIs [−7.2, 4.3], [9.2, 12.4], and [−1.2, −0.5]. Inside a table the convention differs, and Tables & Figures covers it: APA gives the interval its own LL and UL columns with the level in the header, so the brackets disappear.

Two things trip people up. The first is that the interval inherits the leading-zero rule of whatever it bounds, so the three patterns from the table above come out differently:

d = 0.96, 95% CI [0.42, 1.49]. Keeps its zeros, because d is unbounded.
r(58) = .34, 95% CI [.09, .55]. Drops them, because a correlation cannot pass 1.
b = 0.42, SE = 0.14, 95% CI [0.14, 0.70]. Keeps them: an unstandardized slope is in the outcome's own units and can be any size at all.

The second is naming what the interval is on. An interval around a mean difference is measured in points, seconds, or millimeters; an interval around d is measured in standard deviations; an interval around r lives on the correlation scale. Writing "95% CI [1.59, 7.01]" without saying it is the difference in word pairs leaves the reader guessing at the units, so APA writes the quantity in: 95% CI of the difference [1.59, 7.01].

Not every effect size gets one in student work. η² and Cramér's V have intervals, but building them takes a noncentral distribution rather than the ordinary formula, which is why the ANOVA and chi-square rows above are so often reported bare. That is a habit rather than a rule: JASP will give you a confidence interval on η² and ω² from the ANOVA's effect-size options, and if your software offers one, report it. Means, mean differences, correlations, and regression coefficients have no excuse at all.

Hunt the errors

Below is a results paragraph a student handed in. It contains eleven APA violations: wrong italics, stray leading zeros, a "p = .000", a missing N, and more. Click any part you think breaks a rule. Correct clicks fix the text and reveal the rule; a few correctly-formatted statistics are salted in to keep you honest.

🔍 Find the 11 APA errors

Click the statistics that look wrong. Green = fixed; the rule appears below. Dotted underlines mark the clickable parts.

APA style is a checklist, not a talent. Every rule here is mechanical: italicize the Latin letters, leave the Greek upright, drop leading zeros only on bounded numbers, floor tiny p-values, and put the SD next to its mean. Run that checklist over your Results section once and you'll fix nearly every formatting mark a grader would take off for.

Keep that checklist on your desk: print the one-page APA reporting cheat sheet, or convert your own numbers with the APA formatter.

Why it matters: correct notation does real work: it's how a reader parses your numbers at a glance. Italic t tells them "test statistic"; the parenthesized df tells them your sample size and design; the absence of a leading zero on p signals "this can't be bigger than 1". Get the typography right and your results read as the work of someone who knows exactly what each number is. Reach for the site's effect-size converter when you need a d, r, or η² to report, and you'll see the same conventions there.

Problem 43 of the practice problems gives you a results sentence whose arithmetic is entirely correct and which still breaks exactly three APA 7 rules.

Common questions

Do I italicize p and t in APA style?

Yes. The rule is simple once you see it: statistical symbols written with Latin letters are italicized, and those written with Greek letters are not. So t, F, r, p, M, SD, d, N, and R² are all italic, while α, β, χ², and η² stay upright, even when they sit right next to an italic Latin symbol (it's R² but η²). The operators and labels around them (the '=' sign, parentheses, 'df', units) are never italicized. Getting this one rule right fixes the most frequently flagged APA error there is.

What is the difference between N and n?

Capital N is the whole sample; lowercase n is a piece of it. So a study of 120 people split into two conditions reports N = 120 once, then n = 60 per group when it describes them separately. Both are Latin, so both are italic, and both keep the distinction in every table heading and figure note as well. The place it matters most is chi-square, which carries the total inside its parentheses: χ²(1, N = 120) = 6.30. A lowercase n there would tell a reader you had tested only one cell. The related habit worth copying: whenever a subgroup analysis drops people, give its own n rather than letting the reader assume the full sample carried through.

My department uses a different style guide. Do these rules still apply?

The typography is APA's and the substance is everyone's. Which letters go italic, whether a number keeps its leading zero, and where the degrees of freedom sit are conventions that other style guides set differently, so follow whichever one your department names. What no guide disagrees about is what has to be there: the test statistic, its degrees of freedom, an exact p-value rather than a threshold, an effect size, and an interval around the estimate. A reader cannot judge your result without those five, whatever the house style dresses them in. If your department publishes no guide at all, use APA and say so once in your methods, which is a defensible choice nobody marks down.