With a sample size of 254, and 254 − 6 − 1 = 247 degrees of freedom, the critical value for a two-tail 95% t-statistic is very close to the two-tail 95% statistic of 1.96. Using this critical value, the formula for the 95% confidence interval for the jth coefficient estimate is:
95% confidence interval = 
. But first we need to figure out the coefficient standard error:
Hence, the confidence interval is 0.1715 ± 1.96(0.08182).
With 95% probability, the coefficient will range from 0.0111 to 0.3319, 95% CI = {0.0111 < b1 < 0.3319}
