Question

you will need the z and t tables.

вопрос 12

select the tcrit for the following situation:
two tail
alpha = 0.05
df = 15

+-1.7531
+-2.1448
+-1.7459
+-2.1314

Explanation:

Step1: Recall t - critical value formula for two - tail test

For a two - tail t - test, the significance level in each tail is $\frac{\alpha}{2}$. Given $\alpha = 0.05$, so $\frac{\alpha}{2}=0.025$. The degrees of freedom $df = 15$.

Step2: Use t - distribution table or calculator

We look up the t - critical value in the t - distribution table (or use a t - critical value calculator) with $df = 15$ and $\alpha/2=0.025$ for a two - tail test. From the t - distribution table, the t - critical value for $df = 15$ and $\alpha = 0.05$ (two - tail) is approximately $\pm2.1314$.

Answer:

$\pm2.1314$ (corresponding to the option + - 2.1314)