Question: An Oklahoma transportation planning group is concerned about the lack of car-pooling on the part of commuters. They are afraid that the proportion of Oklahoma drivers car-pooling is below the national average of 20%. A survey of 356 Oklahoma drivers reveals that 18.7% of them car pool. Test at the 5% significance level the null hypothesis that the proportion of Oklahoma drivers car-pooling is at least the national average of 20%. That means to do a left-sided test for the population proportion.