Chapter 9 - Statistics Flashcards
What two things do statistics inform about?
- Reliability
2. Meaningfulness
What are the most fundamental components of most statistical techniques?
Measures of central tendency and variability.
What does the nominal level of measurement provide info about?
About difference, but not much more. It is used to name, identify, or classify into categories.
What does the ordinal level of measurement provide info about?
Shows direction of difference, but we do not know amount of difference. Numbers indicate rank or order, allow for greater or less than.
What does the interval level of measurement provide info about?
The intervals or distances between numbers, but it is not known how far any of the numbers are from zero. There is an equality of units, but no true zero.
What does the ratio level of measurement provide info about?
Each number can be thought of as a distance measured from zero.
What does the absolute zero point in the ratio level of measurement represent?
It represents the absence of the variable being measured.
What is non-parametric data?
Data that does not meet the assumption of normality.
i.e. Nominal, ordinal levels.
What is parametric data?
Data that does meet the assumption of normality.
i.e. Interval, ration levels.
What does variability estimate and what is its formula?
It is the best estimate of the spread of scores.
s^2 = The sum of ((X - Xav)^2) / (N - 1)
What are the levels of a normal distribution?
+1 sd = 68%
+2 sd = 95%
+3 sd = 99%
What does positive skewness look like?
Peak near the y-axis.
What does negative skewness look like?
Peak far away from the y-axis.
What does kurtosis represent?
Peakedness of distribution.
What does the leptokurtic distribution look like?
Strong peak.
What does the platykurtic distribution look like?
No peak, close to even distribution throughout.
What does correlation measure?
A measure of the strength of the relationship between two variables, X and Y.
What does the pearson product-moment correlation assume?
That the X and Y variables are normally distributed and are interval or ratio scale scores.
What is the spearman rank-order correlation used for?
It is used for ordinal scale data, or interval or ration scale data that deviate substantially from normality.
What is the pearson r relationship independent of?
- The # of scores.
- The size of scores.
- The dispersion of scores.
What is pearson r derived from?
Covariance.
What is covariance?
How much the deviations in the mean of your X variable related to the deviations in the mean of your Y variable.
Null Hypothesis:
The observed correlation is due to error.
When is r significant?
When it meets or exceeds the tabled critical value of r.
