Descriptive Statistics
What is the difference between Sample and Population?
Sample is a subset of the population set.
What is the mode
{2, 4, 5, 6, 5}
5
What is a Quartile?
A point in an ordered data set that divides the distribution into four equal parts, each representing 25% of the data.
True or False: The last entry in a cumulative frequency table equals the total number of data values.
True
What do the upper and lower values represent in Sigma notation?
Lower: the position where the sum starts.
Upper: the position where the sum ends.
Which measure of spread is defined as the sum over a sequence devided by the amount of elements in the sum?
Mean (average)
Find the median
{8, 2, 5, 1, 4}
4
Which quartile represents the 50th percentile?
Q2 or median
From a cumulative frequency graph, how can you estimate the median?
By finding the "n/2" th value (50th percentile).
Write the sum of 1+2+3+4+5 in Sigma notation.
Σ5i=1(i)
What type of data consists of names, labels or categories?
Qualitative (categorical) data.
A student’s test scores are 70, 75, 80, and 85. What is the mean?
77.5
What does the IQR (Inter Quartile Range) measure?
It measures the spread of the middle 50% of the data.
If 12 students scored ≤ 50 points and 25 students scored ≤ 60 points, how many scored between 51 and 60?
25-12=13
compute Σ4k=1(k2).
30
What is the sampling technique that sellects by a proportion-representation metric?
Stratified Sampling
Which measure of central tendency is most affected by outliers?
Mean
Given a data set of 30 ordered values, find the Q1 and Q3 positions for this data set.
Q1=7.75 (between 7th and 8th)
Q3=23.25 (between 23rd and 24th)
A class of 40 students has a cumulative frequency of 30 at 70 marks. What does this mean?
It means that 30 students scored up to 70 marks ( 30 students got ≤70 marks)
or
10 students got between 70 and 100 marks
Compute Σ6i=2(A), where A{12, 5, 6, 5, 4, 1, 3, 5, 7}
24
If data is skewed right, will the mean be greater than, less than, or equal to the median?
Greater than.
A dataset has a mean of 20 and the sum of all values is 220. How many data points are there?
11
The values {2, 4, 6, 8, 10, 12, 14} have an interquartile range (IQR) of ______.
8 (Q3=12, Q1=4)
From a cumulative frequency curve out of 100 test scores:
20 students scored below 40
50 students scored below 70
75 students took the test
How many students scored between 40 and 70?
30
If Σ10i=1(xi) = 250, what is the mean of the total amount of values being summed?
25