| This is a graded assignment reflecting your own work only. Students are not permitted assistance from other students or tutors. |
| 7. (4 pts) A tech service hot line call center is concerned about the duration of inbound calls. You have been |
| tasked with compiling and analyzing the center's call data, below, representing a sample of 250 calls from |
| a day's inbound call volume. |
| Customer ID | Call date | Call duration |
| 125260805 | 10/1/10 | 32 | | a. Calculate the sample mean and standard deviation for call duration time. |
| 125265384 | 10/1/10 | 163 |
| 125266412 | 10/1/10 | 7 |
| 125267836 | 10/1/10 | 29 |
| 125281795 | 10/1/10 | 84 |
| 125282733 | 10/1/10 | 60 |
| 125284950 | 10/1/10 | 36 | | b. Calculate a 95% confidence interval for the mean call duration |
| 125286575 | 10/1/10 | 76 | | from the sample data. |
| 125292230 | 10/1/10 | 85 |
| 125300266 | 10/1/10 | 52 |
| 125306688 | 10/1/10 | 39 |
| 125311602 | 10/1/10 | 101 |
| 125313493 | 10/1/10 | 194 |
| 125316250 | 10/1/10 | 283 | | c. Six months ago, the average call duration was 126. Based on the finding |
| 125320565 | 10/1/10 | 173 | | of your confidence interval, is it reasonable to say that call duration has |
| 125323846 | 10/1/10 | 88 | | not changed from 6 months ago? |
| 125329947 | 10/1/10 | 61 |
| 125335633 | 10/1/10 | 26 |
| 125335970 | 10/1/10 | 78 |
| 125336423 | 10/1/10 | 41 |
| 125339446 | 10/1/10 | 64 |
| 125340538 | 10/1/10 | 267 |
| 125343444 | 10/1/10 | 16 |
| 125356293 | 10/1/10 | 226 |
| 125365638 | 10/1/10 | 36 |
| 125369580 | 10/1/10 | 46 |
| 125370308 | 10/1/10 | 29 |
| 125384797 | 10/1/10 | 65 |
| 125384981 | 10/1/10 | 94 |
| 125391046 | 10/1/10 | 193 |
| 125400997 | 10/1/10 | 27 |
| 126019495 | 10/1/10 | 94 |
| 126019725 | 10/1/10 | 37 |
| 126021634 | 10/1/10 | 152 |
| 126022692 | 10/1/10 | 149 |
| 126029251 | 10/1/10 | 34 |
| 126031108 | 10/1/10 | 88 |
| 126035487 | 10/1/10 | 82 |
| 126039091 | 10/1/10 | 96 |
| 126042536 | 10/1/10 | 197 |
| 126043327 | 10/1/10 | 202 |
| 126047171 | 10/1/10 | 31 |
| 126048039 | 10/1/10 | 206 |
| 126055040 | 10/1/10 | 166 |
| 126058266 | 10/1/10 | 20 |
| 126063438 | 10/1/10 | 79 |
| 126070772 | 10/1/10 | 140 |
| 126072359 | 10/1/10 | 255 |
| 126075014 | 10/1/10 | 214 |
| 126079142 | 10/1/10 | 43 |
| 126079523 | 10/1/10 | 107 |
| 126089959 | 10/1/10 | 152 |
| 126109278 | 10/1/10 | 124 |
| 126124189 | 10/1/10 | 334 |
| 126124936 | 10/1/10 | 182 |
| 126127258 | 10/1/10 | 287 |
| 127023310 | 10/1/10 | 14 |
| 127027582 | 10/1/10 | 138 |
| 127027819 | 10/1/10 | 85 |
| 127031444 | 10/1/10 | 38 |
| 127034527 | 10/1/10 | 96 |
| 127037084 | 10/1/10 | 155 |
| 127045175 | 10/1/10 | 51 |
| 127046951 | 10/1/10 | 161 |
| 127049464 | 10/1/10 | 355 |
| 127056442 | 10/1/10 | 260 |
| 127066233 | 10/1/10 | 101 |
| 127067302 | 10/1/10 | 273 |
| 127067709 | 10/1/10 | 91 |
| 127071411 | 10/1/10 | 59 |
| 127072160 | 10/1/10 | 60 |
| 127076815 | 10/1/10 | 322 |
| 127079341 | 10/1/10 | 54 |
| 127080741 | 10/1/10 | 132 |
| 127081898 | 10/1/10 | 118 |
| 127083604 | 10/1/10 | 111 |
| 127084357 | 10/1/10 | 188 |
| 127085675 | 10/1/10 | 82 |
| 127088302 | 10/1/10 | 384 |
| 127091788 | 10/1/10 | 90 |
| 127093911 | 10/1/10 | 60 |
| 127095062 | 10/1/10 | 27 |
| 127099273 | 10/1/10 | 101 |
| 127105571 | 10/1/10 | 81 |
| 128323367 | 10/1/10 | 201 |
| 128326577 | 10/1/10 | 112 |
| 128328618 | 10/1/10 | 73 |
| 128328946 | 10/1/10 | 225 |
| 128333478 | 10/1/10 | 23 |
| 128336825 | 10/1/10 | 17 |
| 128339920 | 10/1/10 | 90 |
| 128341159 | 10/1/10 | 283 |
| 128342774 | 10/1/10 | 99 |
| 128343124 | 10/1/10 | 141 |
| 128344122 | 10/1/10 | 166 |
| 128346866 | 10/1/10 | 199 |
| 128347314 | 10/1/10 | 89 |
| 128352984 | 10/1/10 | 53 |
| 128356370 | 10/1/10 | 114 |
| 128356572 | 10/1/10 | 42 |
| 128358051 | 10/1/10 | 224 |
| 128362446 | 10/1/10 | 75 |
| 128365097 | 10/1/10 | 78 |
| 128367558 | 10/1/10 | 277 |
| 128369246 | 10/1/10 | 42 |
| 128377877 | 10/1/10 | 135 |
| 128378385 | 10/1/10 | 251 |
| 128378722 | 10/1/10 | 83 |
| 128378777 | 10/1/10 | 44 |
| 128378898 | 10/1/10 | 71 |
| 128379494 | 10/1/10 | 158 |
| 128385217 | 10/1/10 | 113 |
| 128385944 | 10/1/10 | 39 |
| 128392375 | 10/1/10 | 122 |
| 128394965 | 10/1/10 | 106 |
| 128398149 | 10/1/10 | 33 |
| 128399158 | 10/1/10 | 251 |
| 128399894 | 10/1/10 | 119 |
| 128400616 | 10/1/10 | 163 |
| 128403961 | 10/1/10 | 113 |
| 128406051 | 10/1/10 | 228 |
| 128412722 | 10/1/10 | 63 |
| 128413720 | 10/1/10 | 231 |
| 128416727 | 10/1/10 | 333 |
| 128418119 | 10/1/10 | 70 |
| 128418262 | 10/1/10 | 58 |
| 128418535 | 10/1/10 | 52 |
| 128418694 | 10/1/10 | 211 |
| 128419896 | 10/1/10 | 163 |
| 128425993 | 10/1/10 | 46 |
| 128426714 | 10/1/10 | 201 |
| 128428865 | 10/1/10 | 240 |
| 128432111 | 10/1/10 | 250 |
| 128434678 | 10/1/10 | 163 |
| 128435786 | 10/1/10 | 336 |
| 128436228 | 10/1/10 | 590 |
| 128436501 | 10/1/10 | 27 |
| 128438058 | 10/1/10 | 103 |
| 128439876 | 10/1/10 | 44 |
| 128440144 | 10/1/10 | 170 |
| 128441504 | 10/1/10 | 374 |
| 128442955 | 10/1/10 | 187 |
| 128443111 | 10/1/10 | 67 |
| 128446681 | 10/1/10 | 110 |
| 128447039 | 10/1/10 | 54 |
| 128447877 | 10/1/10 | 323 |
| 128453999 | 10/1/10 | 113 |
| 128454210 | 10/1/10 | 224 |
| 128454310 | 10/1/10 | 9 |
| 128456505 | 10/1/10 | 157 |
| 128471670 | 10/1/10 | 136 |
| 128472996 | 10/1/10 | 418 |
| 128475207 | 10/1/10 | 238 |
| 128475208 | 10/1/10 | 328 |
| 128475246 | 10/1/10 | 19 |
| 128475419 | 10/1/10 | 42 |
| 128476234 | 10/1/10 | 9 |
| 128477495 | 10/1/10 | 384 |
| 128481456 | 10/1/10 | 97 |
| 128483716 | 10/1/10 | 286 |
| 128484348 | 10/1/10 | 45 |
| 128486146 | 10/1/10 | 108 |
| 128486613 | 10/1/10 | 92 |
| 128486630 | 10/1/10 | 13 |
| 129174563 | 10/1/10 | 179 |
| 129175338 | 10/1/10 | 88 |
| 129175535 | 10/1/10 | 197 |
| 129177268 | 10/1/10 | 167 |
| 129179358 | 10/1/10 | 84 |
| 129179714 | 10/1/10 | 181 |
| 129182188 | 10/1/10 | 173 |
| 129182747 | 10/1/10 | 19 |
| 129190345 | 10/1/10 | 75 |
| 129190534 | 10/1/10 | 59 |
| 129192374 | 10/1/10 | 77 |
| 129192410 | 10/1/10 | 70 |
| 129195867 | 10/1/10 | 131 |
| 129196727 | 10/1/10 | 111 |
| 129198659 | 10/1/10 | 90 |
| 129199122 | 10/1/10 | 44 |
| 129200003 | 10/1/10 | 555 |
| 129203156 | 10/1/10 | 277 |
| 129203472 | 10/1/10 | 169 |
| 129206033 | 10/1/10 | 246 |
| 129206861 | 10/1/10 | 167 |
| 129208795 | 10/1/10 | 91 |
| 129210004 | 10/1/10 | 102 |
| 129212701 | 10/1/10 | 81 |
| 129213812 | 10/1/10 | 52 |
| 129215277 | 10/1/10 | 233 |
| 129220332 | 10/1/10 | 163 |
| 129222158 | 10/1/10 | 124 |
| 129222842 | 10/1/10 | 49 |
| 129224281 | 10/1/10 | 109 |
| 129225679 | 10/1/10 | 223 |
| 129225950 | 10/1/10 | 152 |
| 129226725 | 10/1/10 | 35 |
| 129227699 | 10/1/10 | 96 |
| 129231806 | 10/1/10 | 156 |
| 129233328 | 10/1/10 | 76 |
| 129236895 | 10/1/10 | 96 |
| 129241447 | 10/1/10 | 204 |
| 129242271 | 10/1/10 | 144 |
| 129246314 | 10/1/10 | 248 |
| 129251321 | 10/1/10 | 44 |
| 129252929 | 10/1/10 | 319 |
| 129253189 | 10/1/10 | 75 |
| 129253674 | 10/1/10 | 31 |
| 129254417 | 10/1/10 | 16 |
| 129256893 | 10/1/10 | 166 |
| 129261872 | 10/1/10 | 242 |
| 129264631 | 10/1/10 | 80 |
| 129267699 | 10/1/10 | 164 |
| 129269139 | 10/1/10 | 440 |
| 129269235 | 10/1/10 | 296 |
| 129270130 | 10/1/10 | 34 |
| 129273041 | 10/1/10 | 333 |
| 129276237 | 10/1/10 | 147 |
| 129282675 | 10/1/10 | 113 |
| 129283098 | 10/1/10 | 211 |
| 129287376 | 10/1/10 | 61 |
| 129290376 | 10/1/10 | 118 |
| 129290748 | 10/1/10 | 305 |
| 129294700 | 10/1/10 | 64 |
| 129297693 | 10/1/10 | 36 |
| 129298265 | 10/1/10 | 14 |
| 129299403 | 10/1/10 | 62 |
| 129300494 | 10/1/10 | 73 |
| 129300600 | 10/1/10 | 309 |
| 129300710 | 10/1/10 | 206 |
| 129304950 | 10/1/10 | 132 |
| 129305145 | 10/1/10 | 115 |
| 129308103 | 10/1/10 | 123 |
| 129308705 | 10/1/10 | 39 |
| 129311397 | 10/1/10 | 100 |
| 129316198 | 10/1/10 | 210 |
| 129316735 | 10/1/10 | 190 |
| 129319934 | 10/1/10 | 51 |
| 130001647 | 10/1/10 | 318 |
| 130003599 | 10/1/10 | 21 |
| 130004516 | 10/1/10 | 136 |
| 130005887 | 10/1/10 | 115 |
| 130008705 | 10/1/10 | 49 |
| 130009741 | 10/1/10 | 63 |
| 130010822 | 10/1/10 | 66 |
| 130011295 | 10/1/10 | 170 |
| 130013641 | 10/1/10 | 149 |
| 130014615 | 10/1/10 | 320 |
| 130015446 | 10/1/10 | 24 |
| 130015720 | 10/1/10 | 128 |