An inaccuracy in exercise 8.2 in S&W

You are asked to do a number of statistical analyses using the data provided in the regression table. However, they do not report the number of observations and as we know this could affect the critical values.

We carry on imagining n is "sufficiently large" for the t-distribution to converge to the standard normal. So when doing two-sided tests or constructing confidence intervals at a 5% significance level, use t_c = 1.96

Since the data collected is on houses sold in a particular neighborhood over the past year, this could be quite inaccurate actually. A more likely number of observations lies way lower than convergance, but then again your guess is as good as mine. 

Herman