Study sets, textbooks, questions
Upgrade to remove ads
SYA Chapter 4
Terms in this set (17)
What do we mean by variability?
Variability refers to the extent to which a distribution is spread out or clustered.
What do measures of variability include?
What is range?
Distance between the minimal and maximal
sometimes you might need to consider "real limits"
What is the disadvantage of using range as a measure of variability?
Range is determined by only two scores in the data (min and max scores) and ignore what goes on between the two scores.) Doesn't consider what goes on in the middle.
What is standard deviation?
You first compute distance between each score and the
mean (called "deviation"). In the example below, the
score of "1" has a deviation of 5. Standard deviation is
the average of these distances.
Tells us how spread out or clustered the info is. If its small overall the distance is small (clustered)
How to calculate standard deviation:
Step 1: Compute deviation score for each value.
- Deviation Score = X - μ
(note: X is each score, and μ is the mean).
Step 2: Square each deviation score.
Step 3: Sum squared deviation scores to get sum of squares (SS).
- SS = Σ(X - μ)2
Step 4: Divide SS by N to get variance (σ2).
Step 5: Square root variance to get σ
standard deviation of the population we use...
for variance of population we use
σ^2 (sigma squared)
standard deviation of the sample we use
standard deviation of the sample we use...
When you take a sample from a population, which part of the distribution are you most likely to select scores from? (Fig. 4.5, p.99).
More like to select scores around the center because there
are more cases there.
Why is this phenomenon important for computing sample
The cases you select tend to have score that are similar to each other (i.e., around the average).Therefore, you tend to
underestimate the variability when taking a sample, instead of using the population data.
the formulas for sample variance and standard deviation is....
very similar. The difference is that you use n-1, instead of n
write the formula for sample variance
write the formula for sample standard deviation
What happens to the standard deviation when you add a constant to each score?
Standard deviation does not change. Imagine a
histogram. By adding a constant, you are moving
the whole distribution to the right without changing
the width of the distribution.
What happens to the standard deviation when you multiply each score by a constant?
Standard deviation will be multiplied by the constant. Imagine that you are stretching the histogram and making wider.
Sets with similar terms
HIM 505 Chapter 3
Variability stats ch 4
Other sets by this creator
SYA Chapter 5
SYA Chapter 3
SYA Chapter 2
Other Quizlet sets
Trastornos de Ansiedad
Perio: 3, 5, 13, 14, 15, 20
Community / Mental Final
BIO 1108 CH 27 HW