# Data Science Questions and Answers – Summarizing and Merging Data

This set of Data Science Multiple Choice Questions & Answers (MCQs) focuses on “Summarizing and Merging Data”.

1. Which of the following function gives information about top level data?
b) tail
c) summary
d) none of the mentioned

Explanation: The function head is very useful for working with lists, tables, data frames and even functions.

2. Point out the correct statement.
a) head function work on string
b) tail function work on string
c) head function work on string but tail function do not
d) none of the mentioned

Explanation: Both head and tail function do not work on strings.

3. Which of the following function is used for quantiles of quantitative values?
a) quantile
b) quantity
c) quantiles
d) all of the mentioned

Explanation: In probability and statistics, the quantile function specifies, for a given probability in the probability distribution of a random variable, the value at which the probability of the random variable will be less than or equal to that probability.

4. Which of the following function is used for determining missing values?
a) any
b) all
c) is
d) all of the mentioned

Explanation: In R, missing values are represented by the symbol NA.

5. Point out the wrong statement.
a) Common variables are used to create missingness vector
b) Common variables are used to cutting up quantitative variables
c) Common variables are not used to apply transforms
d) All of the mentioned

Explanation: Common variables are not used to apply transforms.

6. Which of the following transforms can be performed with data value?
a) log2
b) cos
c) log10
d) all of the mentioned

Explanation: Many common transforms can be applied to the data with R.

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7. Each observation forms a column in tidy data.
a) True
b) False

Explanation: Each variable forms a column in tidy data.

8. Which of the following function is used for casting data frames?
a) dcast
b) ucast
c) rcast
d) all of the mentioned

Explanation: Use acast or dcast depending on whether you want vector/matrix/array output or data frame output.

9. Which of the following join is by default used in plyr package?
a) left
b) right
c) full
d) all of the mentioned

Explanation: Join is faster in plyr package.

10. mutate function is used for casting as multi dimensional arrays.
a) True
b) False

Explanation: mutate is used for adding new variables.

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