11: Give it a try

As the hotshot fish food innovator who has just shown how effective your new fish food is, you would really nail down your case if you could show that other brands don’t have your edge. How about practising with a few more t-tests?

Here’s the MKart brand. See if you can remember each of the calculations to blast this one out of the water. Take the information in the first three columns and see if you can calculate all the other columns from that.

  n mean difference of means SD* SEM* SEDM* tcalc



MKart Brand  5 192g
15g 6.7g
Generic Brand  5 173g 20g 8.9g

*SD- standard deviation; SEM- standard error in the mean; SEDM- standard error in the difference of the means

So, are the two brands different, statistically speaking?

Not by a long shot! That’s right, the calculated t value, 1.7, is much less than the critical t value of 2.8. Even though the MKart fish grew a little more, it could easily be due to chance.