Instruction 15-11
Recent Studies Have Found That Australian Children Are

Instruction 15-11
Recent studies have found that Australian children are more obese than in the past.The amount of time children spent watching television has received much of the blame.A survey of 100 ten-year-olds revealed the following with regards to weights and average number of hours a day spent watching television.You are interested in testing whether the average number of hours spent watching TV and weights are independent at 1% level of significance.
| TV Hours |
$$\begin{array} { | l | c | c | c | c | } \hline \text { Weights } & 0 - 3 & 3 - 6 & 6 + & \text { Total } \\\hline \text { More than } 10 \text { kg overweight } & 1 & 9 & 20 & 30 \\\hline \text { Within } 10 \mathrm {~kg} \text { of normal weight } & 20 & 15 & 15 & 50 \\\hline \text { More than } 10 \mathrm {~kg} \text { underweight } & 10 & 5 & 5 & 20 \\\hline \text { Total } & 31 & 29 & 40 & 100 \\\hline\end{array}$$
-Referring to Instruction 15-11,the degrees of freedom of the test statistic are

A) 9.
B) 1.
C) 4.
D) 2.