Question

Now, suppose you run the following:

merged2 <- left_join(students2, students1)

Which one of the following options below is true regarding the number of observations in merged2?

Group of answer choices

(A) There are less than 7,000 observations in merged2.

(B) There are more than 10,000 observations in merged2.

(C) There are exactly 7,000 observations in merged2.

(D) There are exactly 10,000 observations in merged2.

(E) Without more information, we can’t know how many observations are in merged2.

Answer 1

Left Join will returns all observations from the left table and the matching observations from the right table. If no matching observations found in the right table, NULL are used. Thus, merged2 will contain 10,000 observations of students2 with fields UBC_ID, last_name, first_name and gpa. The last_name, first_name will be populated for common 3,000 observations from students1. Rest of 7000 observations have null last_name, first_name .

D) There are exactly 10,000 observations in merged2.