Question

"The Surgeon General's Report on Physical Activity and Health brings together overwhelming evidence linking physical activity (PA) to numerous health benefits and provides a solid foundation upon which to promote regular PA for citizens of all ages. . . . Accordingly, the leisure time activity patterns of adolescent boys and girls [in Iowa] were studied in order to gain a better understanding of the habitual PA patterns in this population. Data were collected from 6,025 children in grades 4 through 12 during fall 1996 using a self-report questionnaire administered during physical education classes. Depending upon age and gender, anywhere from 5% to 15% of Iowa youth report being completely sedentary. Contrary to the findings of most national-scope studies, there was little difference in the extent of participation in PA for boys and girls. Overall, approximately 58% of Iowa boys and 54% of Iowa girls report participating in PA 3 or more days per week for 30 min or more per occasion, figures that are far short of the national health goal of 75%. Findings also reveal that participation in leisure-time PA declines substantially with age." (Hensley and Major, RQES, March 1998, A-33)

What is the dependent variable in this study?

There are two independent variables in this study. Name them.

What was the authors' conclusion regarding the null hypothesis for each independent variable?Hypothesis One

State the null hypothesis.

Identify the decision (accept/reject).

What is the basis for the decision?

Hypothesis Two

State the null hypothesis.

Identify the decision (accept/reject).

What is the basis for the decision?

if the null hypothesis is there is no difference in extent of physical activity between boys and girls ....would you accept the null ?

Answer 1

In the given problem,

The dependent variable: Participation in leisure-time PA

Independent variables: Number of days PA per week, Average number of hours spent in PA per occasion

Null Hypothesis 1: Percentage boys paticipation in leisure-time PA is greater than or equal to 75%

Alternative hypothesis 1: Percentage boys paticipation in leisure-time PA is less than 75%

On the basis of the findings, the author rejected the null hypothesis 1.

Basis of the decision:

approximately 58% of Iowa boys participated in PA 3 or more days per week for 30 min or more per occasion where as national health goal was 75%

Null Hypothesis 2: Percentage girls paticipation in leisure-time PA is greater than or equal to 75%

Alternative hypothesis 2: Percentage girls paticipation in leisure-time PA is less than 75%

On the basis of the findings, the author rejected the null hypothesis 2.

Basis of the decision:

approximately 54% of Iowa girls participated in PA 3 or more days per week for 30 min or more per occasion where as national health goal was 75%

Suppose, there was null hypothesis that there is no difference in extent of physical activity between boys and girls,

still we can not conclude readily on this, because we donot have the acual number of boys and girls out of 6025 children who were studied in this problem. It is similar to the Simpson's paradox , for further details one can simply check Simpson's paradox.