. The state of Maryland has a healthy children goal for childhood obesity. In the next 5 years, the state has a goal of decreasing the obesity rate to 11.3%. The current population mean obesity rate is 15.6%. After two years of a pilot intervention program in Garrett County Maryland that involves 25 children, the county has measured a mean obesity rate of 14.2%. The standard deviation for this rate is 1.1%. What is the value of the test statistic and is this a significant change at a 0.01 level?

Question

.   The state of Maryland has a healthy children goal for childhood obesity.  In the next 5 years, the state has a goal of decreasing the obesity rate to 11.3%.  The current population mean obesity rate is 15.6%.  After two years of a pilot intervention program in Garrett County Maryland that involves 25 children, the county has measured a mean obesity rate of 14.2%.  The standard deviation for this rate is 1.1%.  What is the value of the test statistic and is this a significant change at a 0.01 level?

a)	Statistic = -6.37, no it is not significant
b)	Statistic = -6.37, yes it is significant
c)	Statistic = -19.55, no it is not significant
d)	Statistic = -19.55, yes it is significant
e)	Cannot determine based on information provided

I used a t-test and got A) -6.37, not significant

John · Answer

Using a t-test I agree with -6.37. However, it is significant because -6.37 is a large t-value.

I would never use a t-test when dealing with % which are equivalent to proportions. I would have done a 1 proportion z-test... but given the choices that you were given it looks like your teacher was using a t-test.