Question

1. The average 60-watt (a unit of power) bulb emits about 800 lumens (a measure of brightness) of light. Suppose the population standard deviation is 30 lumens. Also suppose you're testing a new watt bulb to see if it emits more light with the same 60 watts of power. With a sample of 100 bulbs and 99% confidence, what is the minimum average your sample can have and still be counted as statistically significant?

20 points   

QUESTION 6

1. Cassidy wants to know how little excersice someone can do and still lose weight. Suppose she gets 24 volunteers to do 20 minutes of walking a day for a week. She weighs them before and after the week in question and discovers they lost an average of ten pounds with a sample standard deviation of 18. At 99% significance, what was the result of the test?

   		Not statistically significant because the calculated score was less than the critical score.
   		Not statistically significant because the calculated score was greater than the critical score.
   		Statistically significant because the calculated score was less than the critical score.
   		Statistically significant because the calculated score was greater than the critical score.

Answer 1

SOLUTION 5 n=100

Z critical for 99% is 2.58 For two tailed

Z= Xbar-mu/sigma/sqrt(n)

Z= xbar-800/30/sqrt(100)

2.58= xbar-800/3

2.58*3= xbar-800

xbar= 807.74 is minimum sample mean to be statistically significant.

SOLUTION 6: n=24 xbar=10 pounds and sd=18

t= 10/18/sqrt(24)

t= 10/18/4.90

t= 10/3.67

t= 2.72

Degrees of freedom= n-1=24-1=23

t critical= 2.81

Not statistically significant because the calculated score was less than the critical score..