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# Multiple choice question for engineering

## Set 1

1. The expected value or _______ of a random variable is the center of its distribution.
a) mode
b) median
c) mean
d) bayesian inference

Answer: c [Reason:] A probability model connects the data to the population using assumptions.

2. Point out the correct statement:
a) Some cumulative distribution function F is non-decreasing and right-continuous
b) Every cumulative distribution function F is decreasing and right-continuous
c) Every cumulative distribution function F is increasing and left-continuous
d) None of the Mentioned

Answer: d [Reason:] Every cumulative distribution function F is non-decreasing and right-continuous.

3. Which of the following of a random variable is a measure of spread ?
a) variance
b) standard deviation
c) empirical mean
d) all of the Mentioned

Answer: a [Reason:] Densities with a higher variance are more spread out than densities with a lower variance.

4. The square root of the variance is called the ________ deviation.
a) empirical
b) mean
c) Continuous
d) standard

Answer: d [Reason:] Standard Deviation (SD) is the measure of spread of the numbers in a set of data from its mean value.

5. Point out the wrong statement:
a) A percentile is simply a quantile with expressed as a percent
b) There are two types of random variable
c) R cannot approximate quantiles for you for common distributions
d) None of the Mentioned

Answer: c [Reason:] R can approximate quantiles for you for common distributions.

6. Which of the following inequality is useful for interpreting variances ?
a) Chebyshev
b) Stautaory
c) Testory
d) All of the Mentioned

Answer: a [Reason:] Chebyshev’s inequality is also spelled as Tchebysheff’s inequality.

7. For continuous random variables, the CDF is the derivative of the PDF
a) True
b) False

Answer: b [Reason:] For continuous random variables, the PDF is the derivative of the CDF.

8. Chebyshev’s inequality states that the probability of a “Six Sigma” event is less than :
a) 10%
b) 20%
c) 30%
d) 3%

Answer: d [Reason:] If a bell curve is assumed, the probability of a “six sigma” event is on the order of one ten millionth of a percent.

9. Which of the following random variables are the default model for random samples ?
a) iid
b) id
c) pmd
d) all of the Mentioned

Answer: a [Reason:] Random variables are said to be iid if they are independent and identically distributed.

10. Cumulative distribution functions are used to specify the distribution of multivariate random variables.
a) True
b) False

Answer: a [Reason:] In the case of a continuous distribution, it gives the area under the probability density function from minus infinity to x.

## Set 2

1. Which of the following function is used for loading flat files ?
d) none of the Mentioned

2. Point out the correct statement:
a) XLConnect package has more options for manipulating access files
b) XLConnect vignette package can also be used for manipulating excel files
c) write.xlsx write out an excel file with different argument
d) None of the Mentioned

Answer: c [Reason:] write.xlsx write out an excel file with similar argument.

3. Which of the following is an important parameter of read.table function ?
a) file
c) sep
d) all of the Mentioned

4. Which of the following will set the character that represents missing value ?
a) na.quote
b) na.strings
c) nrows
d) all of the Mentioned

Answer: b [Reason:] na.strings takes a character vector.

5. Point out the wrong statement:
a) data.table inherits from data.frame
b) data.table is written in Java
c) data.table is faster at subsetting and updating data
d) none of the Mentioned

Answer: b [Reason:] data.table is written in C.

6. Which of the following package is used for reading excel data ?
a) xlsx
b) xlsc
d) all of the Mentioned

7. Which of the following can be used to view all the tables in memory ?
a) tables
b) alltable
c) table
d) none of the Mentioned

Answer: a [Reason:] The table function is a very basic, but essential, function to master while performing interactive data analyses.

8. Which of the following function programatically extract parts of XML file ?
a) XmlSApply
b) XmlApply
c) XmlSApplyData
d) All of the mentioned

Answer: a [Reason:] xmlSApply are simple wrappers for tapply and lappy functions.

9. Which of the following package is used for reading JSON data ?
a) jsonlite
b) json
c) jsondata
d) all of the Mentioned

Answer: a [Reason:] The jsonlite package is a JSON generator optimized for the web.

10. Extracting XML is the basis for most web scraping
a) True
b) False

Answer: a [Reason:] XML is particularly used in web applications.

## Set 3

1. Which of the following function is good for automatic splitting of names ?
a) split
b) strsplit
c) autsplit
d) none of the Mentioned

Answer: b [Reason:] strsplit split a character string or vector of character strings using a regular expression or a literal string.

2. Point out the correct statement:
a) gsub is used for fixing character vectors
b) sub is used for finding values like grep
c) grep is used for fixing character vectors
d) none of the Mentioned

Answer: a [Reason:] sub and gsub is used for fixing character vectors.

3. Which of the following function is used for fixing character vectors ?
a) tolower
b) toUPPER
c) toLOWER
d) all of the Mentioned

Answer: a [Reason:] It translates character to lower case.

4. Which of the following metacharacter is used to refer to any character ?
a) %
b) @
c) .
d) All of the Mentioned

Answer: c [Reason:] A dot in function name can mean any of the following: nothing at all; a separator between method and class in S3 method.

5. Point out the wrong statement:
a) Variables with character values should be made less descriptive
b) Variables with character values should usually be made in to factor variable
c) Common variables are used to apply transforms
d) All of the Mentioned

Answer: a [Reason:] Variables with character values should be made more descriptive.

6. Which of the following is used for specifying character class with metacharacter ?
a) [].
b) {}
c) /+
d) All of the Mentioned

Answer: a [Reason:] You can list set of characters to accept a given point in the match.

7. Regular expressions can be thought of as combination of literals and metacharacters.
a) True
b) False

Answer: a [Reason:] Regular expressions have rich set of metacharacters.

8. Which of the following signs are used to indicate repetition ?
a) #
b) *
c) –
d) All of the mentioned

Answer: b [Reason:] * and + are metacharacters for repetition of data.

9. Which of the following function is used for searching text strings by means of regular expression ?
a) grepd
b) grepl
c) gepexpr
d) all of the Mentioned

Answer: b [Reason:] grep , grepl , regexpr , gregexpr and regexec search for matches to argument pattern within each element of a character vector.

10. merge function is used for merging data frames.
a) True
b) False

Answer: a [Reason:] To merge two data frames horizontally, use the merge function.

## Set 4

1. Which of the following is correct formula for total variation ?
a) Total Variation = Residual Variation – Regression Variation
b) Total Variation = Residual Variation + Regression Variation
c) Total Variation = Residual Variation * Regression Variation
d) All of the Mentioned

Answer: b [Reason:] The complementary part of the total variation is called unexplained or residual.

2. Point out the correct statement:
a) A standard error is needed to create a prediction interval
b) The prediction interval must incorporate the variability in the data around the line
c) Investors use the residual variance to measure the accuracy of their predictions on the value of an asset
d) All of the Mentioned

Answer: d [Reason:] In statistics, explained variation measures the proportion to which a mathematical model accounts for the variation of a given data set.

3. Which of the following things can be accomplished with linear model ?
a) Flexibly fit complicated functions
b) Uncover complex multivariate relationships
c) Build accurate prediction models
d) All of the Mentioned

Answer: d [Reason:] Linear models are the single most important applied statistical and machine learning technique.

4. Which of the following statement is incorrect with respect to outliers ?
a) Outliers can have varying degrees of influence
b) Outliers can be the result of spurious or real processes.
c) Outliers cannot conform to the regression relationship
d) None of the Mentioned

Answer: c [Reason:] Outliers can conform to the regression relationship.

5. Point out the wrong statement:
a) The fraction of variance unexplained is an established concept in the context of linear regression
b) “Explained variance” is routinely used in principal component analysis
c) The general linear model extends simple linear regression (SLR) by adding terms linearly into the model
d) None of the Mentioned

Answer: d [Reason:] Linearity refers to a mathematical relationship or function that can be graphically represented as a straight line.

6. Which of the following can be useful for diagnosing data entry errors ?
a) hat values
b) dffit
c) resid
d) all of the Mentioned

Answer: a [Reason:] resid returns the ordinary residuals.

7. Multivariate regression estimates are exactly those having removed the linear relationship of the other variables from both the regressor and response.
a) True
b) False

Answer: a [Reason:] Multivariate Data Analysis refers to any statistical technique used to analyze data that arises from more than one variable.

8. Residual ______ plots investigate normality of the errors.
a) RR
b) PP
c) QQ
d) None of the Mentioned

Answer: c [Reason:] Patterns in your residual plots generally indicate some poor aspect of model fit.

9. Which of the following show residuals divided by their standard deviations ?
a) rstudent
b) cooks.distance
c) rstandard
d) all of the Mentioned

Answer: c [Reason:] rstandard stands for standardized residuals.

10. The least squares estimate for the coefficient of a multivariate regression model is exactly regression through the origin with the linear relationships.
a) True
b) False

Answer: b [Reason:] Multivariate regression adjusts a coefficient for the linear impact of the other variables.

## Set 5

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

Answer: a [Reason:] 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

Answer: d [Reason:] 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

Answer: a [Reason:] 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

Answer: d [Reason:] 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

Answer: c [Reason:] 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

Answer: d [Reason:] Many common transform can be applied to the data with R.

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

Answer: b [Reason:] 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

Answer: a [Reason:] 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