Question

using R program. please show everything

The following data concerns monthly sales of an electronic device for the last year a) Plot sales (y) versus time (t). Is it reasonable to use a least squares trend line to relate y tot b) Use a least squares trend line to predict calculator sales for the next three months (January, February, and March of the next year). Device sales, y Month January February 197 211 March 203 April May June 247 239 269 July August September October 308 262 268 266 November 261 December 288

Answer 1

Solution:

given data,

t	y
1	197
2	211
3	203
4	247
5	239
6	269
7	308
8	262
9	268
10	266
11	261
12	288

a)

y 350 300 250 200 150 100 50 0 0 2. 4 6 8 10 14 12

Yes,it is reasonable to use least square trend line

b)

Using Excel

data-> data analysis-> regression

y^= 203.7424 + 7.3601* t

SUMMARY OUTPUT Regression Statistics Multiple R 0.7825 R Square 0.6122 Adjusted R Square 0.5735 Standard Error 22,1503 Observations 12 ANOVA Significance F df SS MS Regression 0.0026 1 7746.5472 7746.5472 15.7888 Residual 10 4906.3695 490.6369 12652.9167 Total 11 Coefficients Standard Error P-value t Stat Lower 95% Upper 95% 13.6326 Intercept 203.7424 14.9453 0.0000 173.3671 234.1177 7.3601 1.8523 3.9735 0.0026 3.2330 11.4873 t Li

y 299.4242 Jan 13 306.7844 Feb 14 15 March 314.1445