Midterm Flashcards
The difference between the highest and lowest score
Range
A grouping or category defined by a lower and upper limit
Class interval
The true limit
Class boundaries
Middle value or midpoint of a class interval
Best representative of class interval
Class mark
Percentage distribution in every class interval
Relative frequency
Number of observations belonging to a class interval
Class frequency
Tabular arrangement of data by class intervals whose frequency is cumulated
Cumulative frequency distribution
Sum of frequencies for each ci is less than upper class boundary
Less than cumf
Sum of frequency for each ci is greater than lower class boundary
Greater than cumf
Tabular arrangement of data showing proportion in percent of each frequency to the total frequency
Relative frequency distribution
Formula for R
R=HS -LS
Formula for i
i = R/ci
Formula for class mark
Class mark = UL + LL / 2
Formula for rel. freq.
RF = f/n x 100
Rounding rule for i
Round off
Tabular arrangement of the gathered data
Frequency distribution
It is used when the values are not all equally represented
Weighted mean
Formula for wgtd mean
Wgtd mean = wgtd freq / freq
Is found by first adding all the scores and then dividing by the number of scores
Most sensitive and reliable
Mean
Rounding rule for mean
Round off
Properties of mean
Sum of deviations from mean = 0
Total sum of negative deviations = positive deviations
If added or multiplied to each score, mean will also multiply or add
May not exist in the distribution
All variables under investigation are computed
Mean is efficient
Mean is unique
Mean is fulcrum or balance point of distribution
Disadvantages of mean
Mean can take fractional value
Mean is sensitive: strongly influenced by outliers
Uses of mean
Variables are measured at the interval-ratio
Anticipate standard deviation
Is an extremely high or an extremely low data value when compared with the rest of the data values
Outlier
Point on the scale of measurement that divides a series of ranked observations into halves
Median
When n is an odd number
Ex. N=7
Md = 7/2 = 3.5= 4th (rounded up) = 4th score
When N is an even number
Ex. N=6
Md= 6/2=3rd + 4th/2
Properties of median
Positional measure
Most representative average
Most reliable in open-ended distribution
Unique
Exists in any distribution
Uses of median
Variables are measured in ordinal or interval-ratio level when distribution is skewed
More stable measure of central tendency is needed
Point on the measurement scale with the maximum frequency
Mode
40,45,46,47,47,48,49,50
Mo=
47
40,45,47,48,49,50
No mode.
It is wrong to say 0
40,40,42,42,44,44,45,47
Mo=
40,42
Bimodal
Properties of mode
Used for nominal data
Center of concentration
Does not always exist
Not always unique
Does not take into consideration all values
Uses of mode
Quickest estimate of central value
Report most common score
Properties of range
Simplest measure of dispersion
Easiest to understand
Rough estimate of variability
Average of the squares of the distance of each value from mean
Variance
Square root of variance
Deviation
Used of variance and deviation
Determine spread of data
Consistency of variable
Used inferential statistics
Determine number of values that fall within specified intervals
Minimum value of 0
Divide distribution into 4 parts
Quartiles
How many quartiles
3
Divide distribution into 10 equal parts
Decile
Values that divide distribution into 100 parts
Percentiles
Scores above mean
Scores below mean
+ deviation
- deviation
