GMAT Quant Chapter 13: Statistics Flashcards
How do we calculate the inclusive number of values in a given set?
Largest number in the set – Smallest number in the set + 1§
How can we count the number of consecutive multiples in a range?
Highest number divisible by our multiple - Lowest number divisible by our multiple + 1
How do we count the number of consecutive integers in a set but only include either the maximum or minimum value?
Highest value in the set – Lowest value in the set.
What are the 2 methods we can use to calculate the arithmetic mean?
Bookend method. If evenly spaced, add first & last values then divide by 2.
Balancing point method. Imagine a number line, Avg is in the middle.
How do we count the number of multiples of either of 2 integers in a set of consecutive integers?
Number of Multiples of A or B h = number of multiples of A + number of multiples of B – the number of multiples of LCM (A,B)
How do we calculate the number of multiples of 2 integers in a given set but no multiples of both of those integers?
Number of multiples of A in the set + Number of multiples of B in the set – 2(number of multiples of LCM(A,B)§
What is the simple formula for the weighted average?
Weighted average =
Sum of Weighted Terms
/
Total Number of Weighted Terms
If we have an odd amount of values in the set, what characteristic will the median value have?
If we have an even amount of values in the set, what characteristic will the median value have?
Odd amount > median is an integer
Even amount > median is a decimal
When does the median = the mean in a given set?
When we have an evenly spaced set
How can we calculate the position of the median value if we have the numbers ordered numerically? (odd + even amount in set)
N terms in a set, N is ODD:
(N+1)/2
N terms in a set, N is EVEN:
avg of terms at N/2 & (N+2)/2 positions.
What kind of set, does not have a mode?
When each value in the set is unique.
Does adding or subtracting the same value to all elements in the set change the standard deviation?
Does multiplying or dividing the data set by the same factor change the standard deviation of a set?
No.
Yes. The standard deviation will change by the factor of that constant value. Dividing reduces, Multiplying increases.
What do we know when the range of a given set is 0?
What do we know when the smallest value in a set is equal to the largest value in a set?
What do we know if the range does not have a 0 standard deviation?
All the values in the set are the same.
The standard deviation is 0.
The largest or smallest value in the set is not equal to the mean.
How do we calculate the weighted average of different values?
(ratio of XX)+(ratio of YY)+(ratio of Z*Z) = weighted average value.
What is the simple formula for an average?
average value of the set = sum of the values in the set / number of values in the set
If we have 2 of any of these, we can work out the missing one.
