CASE FILE
UC Berkeley · Graduate Division · Fall 1973

Berkeley's six biggest departments admitted 45% of men and 30% of women. Look inside each department and women did better in 4 of 6.

Both statements are true. The data is real, the arithmetic is right, and the 14 point gap still does not mean what it seems to mean.

44.5%of 2,691 men admitted (1,198)
30.4%of 1,835 women admitted (557)

Pooled over departments A to F. A lawsuit-sized gap: if you only saw this, you would suspect bias.

Step 1 · your call

In how many of the six departments did men have the higher admission rate?

Remember, men lead by 14 points overall. Make a guess before you open the files.

Step 2 · open the files

Pooled, or department by department

MenWomendot area = applicants

Tap a department to see its numbers.

Step 3 · find the cause

Change where women apply, keep every department's own admission rate

Departments A and B admitted about 6 in 10 applicants. Departments E and F admitted 25% and 6%. Move the slider to give women the same spread of applications across departments as men, and nothing else.

women's actual mix0%men's mix
30.4%women admitted with this mix
44.5%men admitted (their own mix)

men: share of applicantswomen (this mix)letter + % = dept admission rate

Step 4 · what it means

The department is hiding in the average

This is Simpson's paradox: a trend in the combined data that reverses inside every subgroup, or in most of them. Women were applying in far larger numbers to departments that turn most people away (C, D, E, F took 93% of the 1,835 women's applications, against 49% of the men's), and those departments were hard for everybody.

That does not prove the university was fair. It moves the question: why did applications split along gender lines before anyone reached the admissions committee? The 1975 study in Science found that the pooled gap came from how applications were distributed across departments and, after correcting for that, a small bias in women's favour (as summarised by Wikipedia, see Sources).

The rule of thumb: before you compare groups, ask which hidden variable decides who ends up where.

All 24 numbers (the full data set)

Sources