Edexcel AS Level Statistics Complete Exam Bank 250 Multiple Choice
Questions with ANSWER Key and Rationale
QUESTION 1:
Which of the following is NOT a measure of central tendency?
A) Mean
B) Median
C) Mode
D) Standard deviation
ANSWER: D
Rationale: Standard deviation is a measure of spread (dispersion), not central tendency.
The mean, median, and mode all measure the center of a data set.
QUESTION 2:
For a symmetrical distribution, which statement is true?
A) Mean > Median > Mode
B) Mean = Median = Mode
C) Mean < Median < Mode
D) Mean ≠ Median ≠ Mode
ANSWER: B
Rationale: In a perfectly symmetrical distribution, the mean, median, and mode are all
equal. This is a key property of symmetric distributions like the normal distribution.
,QUESTION 3:
What is the interquartile range (IQR)?
A) The range of the middle 50% of the data
B) The difference between the maximum and minimum values
C) The average distance from the mean
D) The range of the bottom 25% of the data
ANSWER: A
Rationale: The IQR is the difference between the upper quartile (Q3) and lower quartile
(Q1), representing the range containing the middle 50% of the data.
QUESTION 4:
An outlier is defined as a value more than:
A) 1 × IQR above Q3 or below Q1
B) 1.5 × IQR above Q3 or below Q1
C) 2 × IQR above Q3 or below Q1
D) 3 × IQR above Q3 or below Q1
ANSWER: B
Rationale: The standard outlier definition in Edexcel AS Statistics is any value above Q3 +
1.5 × IQR or below Q1 − 1.5 × IQR.
QUESTION 5:
Which measure of spread is most appropriate for data with outliers?
A) Range
B) Variance
C) Standard deviation
D) Interquartile range
ANSWER: D
Rationale: The IQR is resistant to outliers because it only considers the middle 50% of the
data. The range, variance, and standard deviation are all affected by extreme values.
QUESTION 6:
What percentage of data lies within ±2 standard deviations of the mean in a normal
distribution?
A) 68%
,B) 95%
C) 99.7%
D) 50%
ANSWER: B
Rationale: Approximately 95% of observations lie within μ ± 2σ in a normal distribution.
This is one of the key properties students must know for AS Statistics.
QUESTION 7:
What percentage of data lies within ±1 standard deviation of the mean in a normal
distribution?
A) 68%
B) 95%
C) 99.7%
D) 50%
ANSWER: A
Rationale: Approximately 68% (about 2/3) of observations lie within μ ± σ in a normal
distribution.
QUESTION 8:
In a set of data, the mean is 50 and the standard deviation is 5. What is the value of a data
point that is 3 standard deviations above the mean?
A) 55
B) 60
C) 65
D) 70
ANSWER: C
Rationale: A value 3 standard deviations above the mean is 50 + 3(5) = 50 + 15 = 65.
QUESTION 9:
A stem-and-leaf diagram is most useful for:
A) Displaying large data sets
B) Preserving individual data values while showing distribution
C) Showing cumulative frequencies
D) Displaying time series data
, ANSWER: B
Rationale: A stem-and-leaf diagram preserves the original data values while also showing
the shape of the distribution. This is why it's a valuable data representation tool.
QUESTION 10:
Which of the following is NOT a valid sampling method?
A) Simple random sampling
B) Systematic sampling
C) Stratified sampling
D) Convenience sampling (for unbiased results)
ANSWER: D
Rationale: Convenience sampling is a non-random method that can introduce bias.
Simple random, systematic, and stratified sampling are valid random or quasi-random
sampling methods.
QUESTION 11:
In stratified sampling, the sample is:
A) Chosen completely at random
B) Divided into groups based on a characteristic, then random samples taken from each
C) Chosen by taking every nth item
D) Chosen based on availability
ANSWER: B
Rationale: Stratified sampling involves dividing the population into strata (groups) sharing
a characteristic, then taking random samples from each stratum, often in proportion to
their size in the population.
QUESTION 12:
In a simple random sample without replacement:
A) Every member of the population is equally likely to be included
B) Members can be selected more than once
C) The sample is chosen by convenience
D) Every nth member is chosen
ANSWER: A
Rationale: In simple random sampling without replacement, every member of the
Questions with ANSWER Key and Rationale
QUESTION 1:
Which of the following is NOT a measure of central tendency?
A) Mean
B) Median
C) Mode
D) Standard deviation
ANSWER: D
Rationale: Standard deviation is a measure of spread (dispersion), not central tendency.
The mean, median, and mode all measure the center of a data set.
QUESTION 2:
For a symmetrical distribution, which statement is true?
A) Mean > Median > Mode
B) Mean = Median = Mode
C) Mean < Median < Mode
D) Mean ≠ Median ≠ Mode
ANSWER: B
Rationale: In a perfectly symmetrical distribution, the mean, median, and mode are all
equal. This is a key property of symmetric distributions like the normal distribution.
,QUESTION 3:
What is the interquartile range (IQR)?
A) The range of the middle 50% of the data
B) The difference between the maximum and minimum values
C) The average distance from the mean
D) The range of the bottom 25% of the data
ANSWER: A
Rationale: The IQR is the difference between the upper quartile (Q3) and lower quartile
(Q1), representing the range containing the middle 50% of the data.
QUESTION 4:
An outlier is defined as a value more than:
A) 1 × IQR above Q3 or below Q1
B) 1.5 × IQR above Q3 or below Q1
C) 2 × IQR above Q3 or below Q1
D) 3 × IQR above Q3 or below Q1
ANSWER: B
Rationale: The standard outlier definition in Edexcel AS Statistics is any value above Q3 +
1.5 × IQR or below Q1 − 1.5 × IQR.
QUESTION 5:
Which measure of spread is most appropriate for data with outliers?
A) Range
B) Variance
C) Standard deviation
D) Interquartile range
ANSWER: D
Rationale: The IQR is resistant to outliers because it only considers the middle 50% of the
data. The range, variance, and standard deviation are all affected by extreme values.
QUESTION 6:
What percentage of data lies within ±2 standard deviations of the mean in a normal
distribution?
A) 68%
,B) 95%
C) 99.7%
D) 50%
ANSWER: B
Rationale: Approximately 95% of observations lie within μ ± 2σ in a normal distribution.
This is one of the key properties students must know for AS Statistics.
QUESTION 7:
What percentage of data lies within ±1 standard deviation of the mean in a normal
distribution?
A) 68%
B) 95%
C) 99.7%
D) 50%
ANSWER: A
Rationale: Approximately 68% (about 2/3) of observations lie within μ ± σ in a normal
distribution.
QUESTION 8:
In a set of data, the mean is 50 and the standard deviation is 5. What is the value of a data
point that is 3 standard deviations above the mean?
A) 55
B) 60
C) 65
D) 70
ANSWER: C
Rationale: A value 3 standard deviations above the mean is 50 + 3(5) = 50 + 15 = 65.
QUESTION 9:
A stem-and-leaf diagram is most useful for:
A) Displaying large data sets
B) Preserving individual data values while showing distribution
C) Showing cumulative frequencies
D) Displaying time series data
, ANSWER: B
Rationale: A stem-and-leaf diagram preserves the original data values while also showing
the shape of the distribution. This is why it's a valuable data representation tool.
QUESTION 10:
Which of the following is NOT a valid sampling method?
A) Simple random sampling
B) Systematic sampling
C) Stratified sampling
D) Convenience sampling (for unbiased results)
ANSWER: D
Rationale: Convenience sampling is a non-random method that can introduce bias.
Simple random, systematic, and stratified sampling are valid random or quasi-random
sampling methods.
QUESTION 11:
In stratified sampling, the sample is:
A) Chosen completely at random
B) Divided into groups based on a characteristic, then random samples taken from each
C) Chosen by taking every nth item
D) Chosen based on availability
ANSWER: B
Rationale: Stratified sampling involves dividing the population into strata (groups) sharing
a characteristic, then taking random samples from each stratum, often in proportion to
their size in the population.
QUESTION 12:
In a simple random sample without replacement:
A) Every member of the population is equally likely to be included
B) Members can be selected more than once
C) The sample is chosen by convenience
D) Every nth member is chosen
ANSWER: A
Rationale: In simple random sampling without replacement, every member of the
