Unit 2 Flashcards
What is the shorthand for null hypothesis?
H0
What is the shorthand for the alternate hypothesis?
H1
What are the two ways that variables can be defined?
-Dependent
-Independent
What is the definition of dependent variables?
-The property that is measured based on the original observation
What is the definition of independent variables?
Explanatory or factors that are in the model / experiment
What is quantitative data called in SPSS?
Scale
What is continuous data called in SPSS?
Ratio
Describe continuous data.
Infinite number of values between two points.
What is an example of continuous data?
-Length
-Weight
Describe discontinuous data.
-Can also be called meristic
-Is observations that exist on a limited number of values
What is an example of discrete data?
-Number of teeth
-Number of spots
What are examples of categorical variables?
-Ranked or ordinal
-Nominal or non-ordinal
-Binary
Describe ranked / ordinal data.
Data that a has rank
ie. Stress levels, where 0 is no stress and 5 is extremely stressed
-Maturity
Describe nominal / non-ordinal data
-Names
-Varieties
ie. Lough Derg
Describe binary data.
-A type of nominal data
-Yes / no
-Male / female
What are the variable types in SPSS?
-Numeric
-String
What are examples of numeric data in SPSS?
-Numbers
-Date
-Time
What are examples of scale quantitative data in SPSS?
-Interval
-No fixed origin of fixed distance (temperature)
-Ratio
-Fixed origin, fixed distance
(Age yrs) (Length cm)
What are parametric statistics?
-Makes assumptions about the distribution of the data
-Data needs to follow a normal distribution
-Very powerful to detect Type 1 errors
What are non-parametric statistics?
-Does not make assumptions
-Data transformed into ranks
-No distribution
-Less powerful, more conservation
What are the two types of errors in statistics?
-Type 1
-Type 2
What is a type 1 error?
Is a false positive
-Is when a null hypothesis is rejected when it should have been accepted
What is a type 2 error?
Is a false negative
Is when a null hypothesis is accepted when it should have been rejected
What is the central tendency?
- Is a value that attempts to describe a set of data by identifying the central position within the data set
What are the most common measures of central tendency?
-The mean
-The median
-The mode
What is the ideal sample size for the best results when using the Central Limit theorem?
Samples sizes between 30 - 50
-Each sample must be an independent series of random observations
-All sampled from the same population
What is the central limit theorem?
Is that the distribution of sample means from a series of a large number of samples taken from the same population follows a normal distribution.
-Simplified to
The distribution of the sample’s means has an overall mean which is equal to the actual population mean
When the variable is nominal, what is the best measure of central tendency?
-Use the mode
When the variable is ordinal, what is the best measure of central tendency?
-Use the median
When the variable is interval/ratio and not skewed, what is the best measure of central tendency?
-Use the mean
When the variable is interval / ratio and is skewed, what is the best measure of central tendency?
-Use the median
What are measures of variability?
-Numbers that describe the diversity or dispersion in the distribution of a variable
What are the common measures of variation?
-Range
-Interquartile range
Describe the range
-Crude measure of variability
-Minimum and maximum values
-Good at determining data entry errors
Describe the interquartile range
-Uses medians (Boxplots)
-1st quartile
-2nd quartile
-3rd quartile
How much data lies in the 1st quartile?
First 25% of values
How much data lies in the 2nd quartile?
Contains the median
-50%
-Half the values
How much data lies within the 3rd quartile?
-Also called the upper quartile
-75%
What does the sum of squares represent?
-Represents a measure of deviation from the mean
What is variance?
Is a measure of average variation
What does SS stand for?
Sum of squares
What does S^2 stand for?
Variance
What does S stand for?
Standard deviation
What is standard deviation?
Is the squared root of variance (S^2)
What does SEOM stand for?
Standard error of the mean
What does CV stand for?
Coefficient of variation
What is the coefficient of variation?
-Is a percentage ratio
-Has no units
-Measure of relative variation
How is the coefficient of variation calculated?
Standard deviation / mean *100
What does a large confidence interval indicate?
-Larger uncertainty
What are confidence intervals?
-If a sample from a population is very large, the true mean of the population has 95% probability of lying within 1.96 * SE
What does SE stand for?
Standard error of the mean
What happens to variance the larger a sample population is?
-The variance becomes smaller
What are two tests for normality?
-Shapiro-Wilk
-Kolmogorov-Smirnov
What normality test is more suited for sample sizes less than 50?
Shapiro- Wilk
What is skewness?
-Is the degree of symmetry of a distribution around its mean.
-Mean is affected by skewness
What is positive skewness?
Where the tail extends to positive values
What is negative skewness?
Asymmetric tail that extends towards more negative values
What is kurtosis?
Is the relative peak or flatness of a distribution compared with the normal distribution
What does mesokurtic mean?
Normal
What does leptokurtic mean?
-Positive
-Narrow distribution of values
-More observations closer to the mean
What does platykurtic mean?
-Negative
-Wide distribution of values
-High dispersion
When do you reject the null hypothesis?
If the test statistic is less than 0.05
What does Levene’s t-test test for?
-Used to test for homogeneity of variances
What are equal variances required for?
-Is required to perform t-tests and ANOVAs
What ways can you transform data in SPSS?
-SQRT
-Log
-Arcsin
