Question

Suppose that you are a city planner who obtains and sample of 20 randomly selected members of a mid-sized town in order to determine the average amount of money that residents spend on transportation each month (such as fuel, vehicle repairs, and public transit). You do not have the population standard deviation. To 3 decimal places, what is the critical value for the 95% confidence interval

Answer 1

Answer:

The critical value for the 95% confidence interval is z = 1.96.

Step-by-step explanation:

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1-0.95}{2} = 0.025$

Now, we have to find z in the Ztable as such z has a pvalue of $1-\alpha$

So it is z with a pvalue of $1-0.025 = 0.975$, so z = 1.96.

The critical value for the 95% confidence interval is z = 1.96.