Hi,
The answer is c. The sample is biased.
This is because the sample is taken on a single state, an Rebecca reports a statistic about the nation. Her data contains information only of her state. If she lives in a very cold state, there is probably more homeowners using electric heat than in a hot state.
The equivalent expression -
4n + 19
10 + f = 10
-10 -10
f = 10 - 10
f = 0.
