In: Math
The Apex corporation produces corrugated paper. It has collected monthly data from January 2001 through March 2003 on the following two variables:
y= total manufacturing cost per month (In thousands of dollars) (COST)
x= total machine hours used per month (Machine)
The data are shown below.
y | x |
1102 218
1008 199
1227 249
1395 277
1710 363
1881 399
1924 411
1246 248
1255 259
1314 266
1557 334
1887 401
1204 238
1211 246
1287 259
1451 286
1828 389
1903 404
1997 430
1363 271
1421 286
1543 317
1774 376
1929 415
1317 260
1302 255
1388 281
Answer the following question
Fill in the blanks for the following statement: “I am 95% confident that the average manufacturing cost at the Apex corporation for all months with 350 total machine hours is between ____ and ____.”
please show me steps
This problem can be solved using regression.
Following are the steps
1 | calculate regression coefficient using mentioned formula |
2 | calculate yhat using regression formula |
3 | calculate root mean square error(syx) |
4 | calculate standard error for prediction |
5 | calculate t critical |
6 | calculate lower and upper value of interval |
Step 1.
y = a+bx
To calculate a and b
y | x | xy | x^2 | y^2 |
1102 | 218 | 240236 | 47524 | 1214404 |
1008 | 199 | 200592 | 39601 | 1016064 |
1227 | 249 | 305523 | 62001 | 1505529 |
1395 | 277 | 386415 | 76729 | 1946025 |
1710 | 363 | 620730 | 131769 | 2924100 |
1881 | 399 | 750519 | 159201 | 3538161 |
1924 | 411 | 790764 | 168921 | 3701776 |
1246 | 248 | 309008 | 61504 | 1552516 |
1255 | 259 | 325045 | 67081 | 1575025 |
1314 | 266 | 349524 | 70756 | 1726596 |
1557 | 334 | 520038 | 111556 | 2424249 |
1887 | 401 | 756687 | 160801 | 3560769 |
1204 | 238 | 286552 | 56644 | 1449616 |
1211 | 246 | 297906 | 60516 | 1466521 |
1287 | 259 | 333333 | 67081 | 1656369 |
1451 | 286 | 414986 | 81796 | 2105401 |
1828 | 389 | 711092 | 151321 | 3341584 |
1903 | 404 | 768812 | 163216 | 3621409 |
1997 | 430 | 858710 | 184900 | 3988009 |
1363 | 271 | 369373 | 73441 | 1857769 |
1421 | 286 | 406406 | 81796 | 2019241 |
1543 | 317 | 489131 | 100489 | 2380849 |
1774 | 376 | 667024 | 141376 | 3147076 |
1929 | 415 | 800535 | 172225 | 3721041 |
1317 | 260 | 342420 | 67600 | 1734489 |
1302 | 255 | 332010 | 65025 | 1695204 |
1388 | 281 | 390028 | 78961 | 1926544 |
sum(y) =40424,sum(x^2) = 2703831, sum(x) = 8337, sum(x*y) = 13023399
a = 206.8651,b = 4.178798
regression equation : y = 206.8651+4.178798*x
Step2
Calculate yhat for x0= 350
= 206.8651+4.178798*350 = 1669.445
Step3
Calculate RMSE
residual = yhat - y where yhat is calculated by putting value of x in above formula
yhat | residual | residual^2 |
1117.843 | -15.8432 | 251.0057 |
1038.446 | -30.446 | 926.9583 |
1247.386 | -20.3859 | 415.5852 |
1364.392 | 30.60774 | 936.8337 |
1723.769 | -13.7689 | 189.5831 |
1874.206 | 6.794342 | 46.16309 |
1924.351 | -0.35124 | 0.123368 |
1243.207 | 2.792892 | 7.800245 |
1289.174 | -34.1739 | 1167.855 |
1318.425 | -4.42548 | 19.58486 |
1602.584 | -45.5838 | 2077.88 |
1882.563 | 4.436745 | 19.68471 |
1201.419 | 2.580875 | 6.660917 |
1234.85 | -23.8495 | 568.7992 |
1289.174 | -2.17389 | 4.725797 |
1402.001 | 48.99855 | 2400.858 |
1832.418 | -4.41767 | 19.51585 |
1895.1 | 7.90035 | 62.41554 |
2003.748 | -6.74841 | 45.54099 |
1339.319 | 23.68053 | 560.7675 |
1402.001 | 18.99855 | 360.9451 |
1531.544 | 11.45581 | 131.2355 |
1778.093 | -4.0933 | 16.75507 |
1941.066 | -12.0664 | 145.5988 |
1293.353 | 23.64731 | 559.1954 |
1272.459 | 29.5413 | 872.6886 |
1381.107 | 6.892547 | 47.5072 |
Syx = 21.78281
Step4:
calculate standard error for prediction
= 4.227521
here n= 27
step5:
calculate t critical = t table at 0.05 and degrees of freedom = n-2 = 27-2=25
t critical = 2.059539
Step 6:
calculate confidence interval
lower = 1660.738
upper = 1678.151
therefore
Fill in the blanks for the following statement: “I am 95% confident that the average manufacturing cost at the Apex corporation for all months with 350 total machine hours is between 1660.738 and 1678.151.”