- #1

- 13

- 0

12 occasions. The results are summarised below.

Σ(t − 35) = −15

Σ(t − 35)^2 = 82.23

Calculate the mean and standard deviation of these times taken to do the crossword.

My real problem is finding out the value of t. or can we find the answer without finding t??. I took t-35 as y, and hence got y's mean as -1.25. Then I am stuck.

I can't make head or tail of the answer provided for the mean:( why do we deduct 35 -1.25?)

Answer

mean = 35 – 15/12

= 33.75 (33.8) minutes

sd = 82.23/12 ( 15/12)

= 2.3 minutes