Update:
OK, IT tells me they've sent instructions already for SPSS trial version download. Great. Then this homework turns oput to be much easier than I had first imagined. Good. Some of the gyan on re-coding and transforming data for the T-test elaborated below would still hold, I guess.
Hi all,
1. Pls let me know if there are any queries etc you're facing w.r.t. session 6 homework. Shouldn;t take more than an hour odd, by my reckoning but if you've no clue on how to approach the questions, then it can seem quite daunting, I now realize.
2. I'll present my own solution to this homework in class in a few slides.
3. The most common -sensical approach, the way I see it for the first two questions is to take out the four concerned columns in a fresh worksheet (and have REspondent ID also to keep count), build pivots and run chisq.test() in R on the pivots obtained. In Excel, you'll need to also generate the expected distribution. This is done as (row total* column total)/(overall total) for each cell in the table. As a general rule, ignore blanks and non-standard responses in your cross-tabs.
4. For the t-test question, you'll need to re-code data into metric (interval) form. So use CTRL+H or 'Find and replace' function in Excel to transform the text responses obtained into a 1-5 scale (or a -2 to 2) scale or something. Sort the responses to weed out blanks and other such. Then run the simple TTEST() function in Excel.
5. The above is only 1 way of doing these things. It seemed to me to be a common-sensical approach and so I elaborated on it. You may reach the answers in a quicker, smarter way, perhaps. That is entirely fine too.
Hope that helps. Pls use the comments thread below for Q&A in case of any queries.
Sudhir
OK, IT tells me they've sent instructions already for SPSS trial version download. Great. Then this homework turns oput to be much easier than I had first imagined. Good. Some of the gyan on re-coding and transforming data for the T-test elaborated below would still hold, I guess.
Hi all,
1. Pls let me know if there are any queries etc you're facing w.r.t. session 6 homework. Shouldn;t take more than an hour odd, by my reckoning but if you've no clue on how to approach the questions, then it can seem quite daunting, I now realize.
2. I'll present my own solution to this homework in class in a few slides.
3. The most common -sensical approach, the way I see it for the first two questions is to take out the four concerned columns in a fresh worksheet (and have REspondent ID also to keep count), build pivots and run chisq.test() in R on the pivots obtained. In Excel, you'll need to also generate the expected distribution. This is done as (row total* column total)/(overall total) for each cell in the table. As a general rule, ignore blanks and non-standard responses in your cross-tabs.
4. For the t-test question, you'll need to re-code data into metric (interval) form. So use CTRL+H or 'Find and replace' function in Excel to transform the text responses obtained into a 1-5 scale (or a -2 to 2) scale or something. Sort the responses to weed out blanks and other such. Then run the simple TTEST() function in Excel.
5. The above is only 1 way of doing these things. It seemed to me to be a common-sensical approach and so I elaborated on it. You may reach the answers in a quicker, smarter way, perhaps. That is entirely fine too.
Hope that helps. Pls use the comments thread below for Q&A in case of any queries.
Sudhir
Dear Prof Sudhir:
ReplyDeleteWhen performing the Chi-square test, how do we create the expected distribution? The class notes say (nr * nc)/total. I could not understand what it means?
For Nike dataset, the expected distribution to use in Excel is (10.1, 5.3, 8.5 and 8.9, 4.7, 7.5). Could you please elaborate a bit!
Thanks,
Raman
Hi Raman,
ReplyDeleteThe addendum slides deck I sent shows how to do this in some detail. Basically, I do not intend for folks to have to wrestle with this level of detail in the stats procedures at all. Ideally, SPSS will handle it all. R also handles it automatically from the cross-tab.
If its not happening, let it be. Use SPSS when you install it.
Sudhir