Assume that an electric supplier is conducting a study to investigate whether the annual residential
electricity consumption has changed in 2019 from previous years. As part of the study, 25 single-person
households were randomly selected. These households consumed the following amounts of electricity
in 2019.
1471, 1727, 1648, 1425, 1334, 1546, 1569, 1544, 1568, 1664, 1590, 1676, 1803, 1281, 1739, 1600,1572, 1413, 1295, 1346, 1599, 1740, 1407, 1746, 1246
The population distribution is assumed to be normal with a known standard deviation of sigma = 160
kWh.
Construct a 90% confidence interval for the population mean of the yearly electricity consumption
of a single-person household. State the confidence interval and calculate the error bound.
If the electric supplier wishes to increase the level of confidence to 95% while keeping the error
bound the same by taking another survey, what changes should it make?
If the electric supplier did another survey, kept the error bound the same, and only surveyed 20
people, what would happen to the level of confidence? Determine the new confidence level.
