Markets have become interested in the potential of social networking sites. But
ID: 3372045 • Letter: M
Question
Markets have become interested in the potential of social networking sites. But they need to understand the demographics of social networking users. A research company conducted a survey in late 2012 that asked about social networking over several years and for different age groups. A table of responses is shown to the right
May 2010 Aug 2011 Aug 2012 total
18-29 274 280 309 863
30-49 323 352 379 1054
50-64 258 282 321 861
Total 855 914 1009 2778
-----The expected values are:
18-29: 265.61 283.94 313.45
30-49 324.40 346.78 382.82
50-64 264.99 283.28 312. 72
a) Compute the x2 statistic
b) How many degree of freedom foes x2 statistic have?
c) Find the critical value where alpha = 0.05
Explanation / Answer
applying chi square test on above data:
a) x2 statistic =0.915
b)degree of freedom =(rows-1)*(column-1)=(3-1)*(3-1)=4
c) for 4 df and 0.05 level critical value =9.488
Observed OBS may -2000 aug-2011 aug-2012 Total 18-29 274 280 309 863 30-49 323 352 379 1054 50-64 258 282 321 861 Total 855 914 1009 2778 Expected Ei=?row*?column/?total may -2000 aug-2011 aug-2012 Total 18-29 265.610 283.940 313.450 863 30-49 324.400 346.780 382.820 1054 50-64 264.990 283.280 312.720 860.99 Total 855 914 1008.99 2777.99 chi square =(Oi-Ei)2/Ei may -2000 aug-2011 aug-2012 Total 18-29 0.27 0.05 0.06 0.38 30-49 0.01 0.079 0.038 0.12 50-64 0.18 0.006 0.219 0.41 Total 0.46 0.14 0.32 0.915