Intro in Stata – Quiz 6

Quiz Question Explanations

Question 1

First summarize total_ely3 to identify the mean value. Then you can create the new binary variable by either manually entering the mean value or using macros:

gen total_ely3_below_avg = (total_ely3 < 10.6438) if total_ely3 != .
or
gen total_ely3_below_avg = (total_ely3 < `r(mean)’) if total_ely3 != .

Macros will be covered in the Stata Best Practices lesson.

Then you just need to count the number of values that are below average.

count if total_ely3_below_avg == 1

Question 2

First summarize total_ely3 to calculate the mean and standard deviation (SD). Then you can either enter these values manually or use macros:

gen total_ely3_std = (total_ely3 – 10.6438)/3.662166 if total_ely3 != .
or
gen total_ely3_std = (total_ely3 – `r(mean)’)/`r(sd)’ if total_ely3 != .

Then just count the number of observations that have values less than 2 for this new variable:

count if total_ely3_std < -2

Question 3

Create a new total_bl variable that takes on values of the original total_bl variable for children in grades 3, 4, and 5 at baseline:

gen total_bl_2 = hindi_bl + math_bl + english_bl if (child_class_bl == 3 | child_class_bl == 4 | child_class_bl == 5)

Then replace the values of this new variable with only Hindi+math scores for children in grades 1 and 2 at baseline:

replace total_bl_2 = hindi_bl + math_bl if (child_class_bl == 1 | child_class_bl == 2)

Now you can take the average of this new variable for children in grades 1 and 2 at baseline:

sum total_bl_2 if (child_class_bl == 1 | child_class_bl == 2)

Question 4

Sorting on total_bl first puts all of the students with the lowest total_bl score at the top. Then sorting on total_ely1 puts the students with the lowest total_ely1 scores at the top of those students with the lowest total_bl scores. But since multiple students have the lowest scores on both tests (total_bl = 3, total_ely1 = 3), Stata will vary which specific student shows up first, unless you included the ‘stable’ option.