A team of environmental scientists measures the concentration of a specific pollutant (in parts per million, ppm) emitted by eight industrial catalytic converters before and after a specific chemical cleaning process. The emission levels are assumed to be normally distributed. The results for the eight converters are shown in the table below:

Converter	$C_1$	$C_2$	$C_3$	$C_4$	$C_5$	$C_6$	$C_7$	$C_8$
Before	42.5	38.8	45.2	40.1	39.5	41.4	43.6	37.9
After	41.3	37.0	43.7	38.0	38.1	39.7	41.7	36.7

Calculate a 98% confidence interval for the mean difference in pollutant emissions.

Use your confidence interval to determine whether there is evidence of a change in the mean pollutant emissions. State your hypotheses clearly and provide a reason for your conclusion.

Converter	$C_1$	$C_2$	$C_3$	$C_4$	$C_5$	$C_6$	$C_7$	$C_8$
Before	42.5	38.8	45.2	40.1	39.5	41.4	43.6	37.9
After	41.3	37.0	43.7	38.0	38.1	39.7	41.7	36.7

Calculate a 98% confidence interval for the mean difference in pollutant emissions.

Use your confidence interval to determine whether there is evidence of a change in the mean pollutant emissions. State your hypotheses clearly and provide a reason for your conclusion.

3.7 Hypothesis Testing with the Normal Distribution

Question 31

Markscheme

3.7 Hypothesis Testing with the Normal Distribution

Question 31

Markscheme

3.7 Hypothesis Testing with the Normal Distribution

Question 31

3.7 Hypothesis Testing with the Normal Distribution Questions

3.7 Hypothesis Testing with the Normal Distribution

Question 31

3.7 Hypothesis Testing with the Normal Distribution Questions