Question

1) Consider a hypothetical study undertaken to determine socio-economic status of lottery ticket buyers. A door-to-door survey of 250 respondents was undertaken between 9AM-5PM during weekdays. Many respondents were not home. From the respondents that were home, questions related to average income, employment status were asked. Does the methodology entail selection bias?

True or False?

-----------------------------------------------------------------

-----------------------------------------------------------------

2) If X, Y are perfectly correlated, Corr(X, Y) could be

a) -1

b) 1

c) 0

d) All the above

-----------------------------------------------------------------

-----------------------------------------------------------------

3) Ventura is a video-gaming company that designs a Multi-player Soccer game. It wants to assess how the game’s reach among the public would be. While looking for volunteers for the study, it states that any true soccer fans should sign up.

This is good sample because the study now has enthusiastic participants.

True or False?

-----------------------------------------------------------------

-----------------------------------------------------------------

4) A Market Research Analyst observes that average price of Spinach increases after average price of Eggs (usually with a lag of one day) increases. Which of the following conclusions cannot be possible

a) Increase in average price of Eggs causes increase in average price of Spinach

b) Increase in average price of Spinach causes increase in average price of Eggs

c) Events of increase in average price of Spinach and average price of Eggs are correlated

d) Events of increase in average price of Spinach and average price of Eggs are related

Answer 1

1) Consider a hypothetical study undertaken to determine socio-economic status of lottery ticket buyers. A door-to-door survey of 250 respondents was undertaken between 9AM-5PM during weekdays. Many respondents were not home. From the respondents that were home, questions related to average income, employment status were asked. Does the methodology entail selection bias?

Yes, the methodology described does entail selection bias. Proper randomization is not being achieved by conducting door to door survey during work timings(9AM-5PM) as most people that would be part of the survey would be unemployed, sick or who are just taking a day off.

2) If X, Y are perfectly correlated, Corr(X, Y) could be

Perfect correlation means that X and Y are perfectly linearly related in the same direction.

3) Ventura is a video-gaming company that designs a Multi-player Soccer game. It wants to assess how the game’s reach among the public would be. While looking for volunteers for the study, it states that any true soccer fans should sign up.

This is good sample because the study now has enthusiastic participants.

This is not a good sample as self selection has taken place, Just stating any true soccer fans to sign up does not mean that they would. Even if a lot of soccer fans turn up does not mean they are the target audience, proper randomization has not being achieved.

4) A Market Research Analyst observes that average price of Spinach increases after average price of Eggs (usually with a lag of one day) increases. Which of the following conclusions cannot be possible

a) Increase in average price of Eggs causes increase in average price of Spinach

Please let me know if anything is unclear in comments. Will reply ASAP. Please upvote if satisfied!