Question

Refer to the accompanying data set of mean drive-through service times at dinner in seconds at two fast food restaurants. Construct a 99% confidence interval estimate of the mean drive-through service time for Restaurant X at dinner; then do the same for Restaurant Y. Compare results.
Construct a 99% confidence interval of the mean drive-through service times at dinner for Restaurant X.
Restaurant X   Restaurant Y
85   104
117   130
119   149
151   119
262   174
183   130
125   114
148   127
157   129
216   130
336   129
308   141
175   227
111   209
151   294
145   123
92   93
233   138
235   240
181   146
155   140
196   206
164   147
120   146
60   134
203   146
181   157
114   131
136   167
174   130
184   238
194   238
227   252
194   234
350   234
307   165
210   88
198   104
183   51
185   168
103   77
147   148
176   144
161   101
172   122
155   144
168   126
119   184
140   154
312   126

Answer 1

In the term t(alpha/2), the accompanied degrees of freedom would everywhere be (n-1), where n= total number of data points. t(alpha/2) = upper alpha/2 point of a Student's t-distribution.