To calculate the degrees of freedom (df) for a one-sample t-statistic, the formula is:

$df = n - 1$

Where $n$ is the number of observations.

Adam has recorded 8 values for the average speed:

$n = 8$

Therefore, the degrees of freedom would be:

$df = 8 - 1 = 7$

Thus, the degrees of freedom for Adam's one-sample t-statistic is 7.

Would you like a detailed explanation on how the t-statistic is used or any further clarifications?

Here are five related questions you might consider:

1. How do you calculate a one-sample t-statistic?
2. What is the interpretation of degrees of freedom in a t-test?
3. How would you calculate the sample mean and standard deviation from the given data?
4. What are the assumptions of the one-sample t-test?
5. How do you interpret the results of a t-test?

Tip: In a t-test, the degrees of freedom impact the shape of the t-distribution, affecting the critical values used for hypothesis testing.