Corrected item-total correlation: what it means and how to read it
In the report: corrected item-total correlation — The correlation of the item with the sum of the other items (the item itself left out of the sum), as SPSS RELIABILITY "Corrected Item-Total Correlation". Empty for an item without spread.
How to read it
How well the item goes along with the rest of the scale. Below about 0.3 the item measures something else: check whether it is reversed or off-topic. Negative — almost always a reversed item.
In plain words
A teacher's quiz had 7 questions, and she wanted to know which ones go along with the rest. For each question she looked at the corrected item-total correlation: how well the answers to that question go along with the total of the other 6, leaving the question itself out. Question 3 came out 0.55, so it goes along with the rest. Question 5 came out close to zero, so it seems to be about something else. Question 6 came out below zero, which almost always means it was asked the opposite way around. A question everyone answered the same gets an empty cell. Now she knows where to look first.
How it is computed
r(xᵢ, Σ xⱼ − xᵢ)Example
The cell with corrected item-total correlation is selected in each report; point at a label to see its note.
- — the sample data (50 rows) the examples use
- — all columns starting with q; includes 'if item deleted'
=STATS_ALPHA(Data!A1:T51, "/^q/", TRUE)
Where you see it
STATS_ALPHA— Computes Cronbach’s Alpha — a measure of internal consistency (reliability) for a set of items, such as Likert-type questions.
Related values
- Cronbach’s alpha — Cronbach’s alpha: how consistently the items measure the same thing, on the rows where every item is answered.
- Standardized alpha — Alpha from the mean correlation of the items, as SPSS "Based on Standardized Items": as if every item had the same variance.
- Alpha if the item is deleted — The alpha (or the standardized alpha) of the remaining items without this one.
Get it in your sheet
One formula in a cell gives the whole report, Corrected item-total correlation included. ALS Stats is a free add-on for Google Sheets™.
Install ALS Stats from Google Workspace Marketplace (opens in a new tab)