Stats I Flashcards
What are the two major statistical methods?
Descriptive stats
Inferential stats
What is descriptive statistics?
Describe collected data
What are inferential statistics?
Estimation and hypothesis testing to make decisions about populations
What are experimental units?
Object upon which we collect data (people, schools, hospitals etc)
What is a population?
All items of interest
What are variables?
Characteristics of individual experiemental units
What is a sample?
Subset of the units of a population
What are parameters?
numbers that summarize data for an entire population
What is a statistic?
numbers that summarize data from a sample, i.e. some subset of the entire population
Samples come from what?
Population or a process
What are the two categories of variables?
Categorical
Quantitative
What is a categorical variable?
The presence of absence of something
The relative weight or rank of the thing that is of research interest
What is a process?
A series of actions or operations that transforms inputs to outputs
What is the nominal scale?
Categories without order
What are ordinal scales?
Nominal variables with an inherent order among the categories
What are interval scales?
Measurable difference or interval or distance between observations
What is a ratio?
Same as interval, but with an absolute reference point
How is qualitative data presented?
Bar graphs
Pie charts
How is quantitative data presented?
Dot plot
Stem & leaf plot
Frequency distribution
What is a summary table?
Lists categories and number of elements in a category
What is a class?
One categories into which qualitative data can be classified
What is class frequency?
The number of observations in the date set falling into a particualr class
What is the class relative frequency?
the class frequency, divided by the total numbers of observations in the data set
What is a class percentage?
the class relative frequency, multiplied by 100
What is a stem and leaf plot?
Tens place on the left hand side of a bar, with ones place of data on the right.
What is a histogram?
bar graph of non-categorical values
What is a dot plot?
Dots on a horizontal scale (Y axis being frequency)
What is a central tendency?
tendency of the data to cluster or center about certain numerical values
What is variability?
Spread of the data
n is notation for what? How about N?
n = sample N = population
Sample mean has what notation?
X bar
Population mean has what notation?
μ
Why is the mean not always the best measure of central tendency?
Affected by extreme values
What happens to the median if there is an even number of values?
average of two central points
What is the value of the median?
Not affected by extreme values
What is the only measure of central tendency that can be used on qualitative variables?
Mode
What is the range?
Measure of dispersion
difference between the highest and lowest values in a given set of values
What is the notation for standard deviation for a sample? Population?
s for sample
Sigma for population
Variance is what?
s^2
Sigma ^2
Why do you subtract 1 from n in the denominator for variance calculations of samples?
Degree of freedom
What does it mean for a bell curve to be symmetric?
Mean=median
if mean
Left skewed
if mean > median, then the bell curve is curved left or right?
Right skewed
1 standard deviation accounts for what percent (in a normal distribution)?
68%
2 standard deviations account for what percent (in a normal distribution)?
95%
3 standard deviations account for what percent (in a normal distribution)?
99.7%
Which scale: simplest level of measurement–categories without order (qualitative)
Nominal scale
Which scale: Nominal variables with an inherent order among the categories (qualitative)
Ordinal
Which scale: Measureable difference or interval or distance between observations
Interval scale
Which scale: measureable or interval distance between observations, with an absolute reference point (such as 0)
Ratio
