When I attempt a t test with Prism, it gives me an error message: "You must have two or more values in each group". But I do. What's wrong?

To perform a t test or one-way ANOVA with Prism, you should format the table for a single column of Y values. Enter the values for each group as a column, so that the replicate values are stacked. You cannot perform a t test when the data are entered in one row with replicates placed side-by-side.