It has been reported that 18.3% of all U. S. households were heated by electricity in 1980, compared to 27.4% in 1995 and 31.5% in 2005. If we are to test whether the population percentage could be equal for these years at the 0.05 level, and assuming a sample size of 1000 U. S. households for each year,

checking my answers

a) what is the degree of freedom? 2
b) what is the critical chi square value? (Specify your answer to 3rd decimal point) 5.991
c) what is the calculated chi square value? (Specify your answer to 4th decimal point) 47.77
d) test whether the population percentages could be equal for these years
Fail to reject the null hypothesis. The population proportions heating with electricity are equal for these years.