PL1010: Research Design and Methods 1B Flashcards
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Categorical variable
Variable with scores that are not on a numeric scale
Descriptive statistics –
Summarise samples – giving someone the main points in a simple form To describe data, we will use graphical and numerical (statistical) techniques
Inferential statistics –
Examine patterns in the data and consider how much data we have You can then draw conclusions about a population based on the analysis of a sample. -> conceptual replication
Summarising
collecting and summarising data
Statistical inference
the ability to draw general conclusions from samples
How many times does a particular score occur?
Percentages/Averages Scores for a particular variable (Frequency statement)
Do scores for one variable correlate with scores for the other variable?
Statement about association
How strong is the correlation or association between two variables?
Statement about association
Do I trust that there is a “genuine” association (relationship)?
Statement about relationship between two variables
Frequency Distribution?
show scores in order and their frequency of appearance in the sample
Negatively skewed
Positively Skewed
When not to describe the skew of data?
When we cannot put our scores in order , from lowest
to highest so when we are describing a categorical
variable with unordered categories
Unimodal?
One major peak
Bimodal
Two major peaks
Approximately symmetrical
How do outliers and the mean relate to each other?
Outliers are extreme values that differ from most values in the data set. Because all values are used in the calculation of the mean, an outlier can have a dramatic effect on the mean by pulling the mean away from the majority of the values.
What happens to the mean, median and mode in a skewed distribution
in normal distributions, they all take on the same number
Why are histograms good?
effective visual summary of a variable’s central tendency and variability
What is a discrete, continuous, independent and dependent variable?
Discrete: variable that is limited (age, gender) Continuous: exists on a continuum basically infinite between highest/lowest IV: variable manipulated/changed to see whether it has an effect on the DV that might change because of the manipulation DV: variable that, though measured, is not being controlled
What is the role of measurement scales?
The numbers don’t necessarily say anything concrete about the objects measured <i>ex.: if I scored high on a test, but someone else scored lower, it’s not necessary because they remembered less even though the data might suggest it → we assume that they mean I remembered more</i>
What is the purpose of a frequency distribution?
Organising data into a meaningful order of how many times
Which variable do I usually find on the X- and Y-Axis in histograms vs. line graphs?
histogram: dv-iv Line/Bar graph: iv-dv
What is the mode, median, mean (+formulas)?
Mode: the highest point in the graph Median: 50th percentileMean: Sum of N/ N
If the mean is slightly larger what does it probably say about or distribution?
Positively skewed
When will the mean and the median be equal?
Symmetric distribution
The benefit of the mode is?
- Representing categorical data * More informative *But not very reflective of the remaining data set
The benefit of the median is?
Not affected by outliers Not stable in comparison and not useful to calculation
What does central tendency refer to?
The scores tendency to distribute in a certain way?
What is the advantage of a bar chart?
- Comparing categories * Mirrors other visualisation techniques were the spread is along the X-axis and the frequency or percentage is along the Y-axis already hints at modality and skewness
What is an alternate name for the y-axis/x-axis?
ordinate/abscissa
Suppose you sell ice cream with three different flavours: chocolate, strawberry and yogurt. The ice cream flavours are measured on a ____________ level. You sell ice cream to children, adults and elderly people. These age groups are measured on a ____________ level.
nominal; ordinal
operational definition
defining a variable in terms of the set of steps or procedures that the researcher goes through in order to manipulate or measure the variable
right skewed
positively skewed
What does a negatively skewed distribution reveal?
A lot of people got close to the maximum score
What does central tendency mean?
average score
Age in months is an example of a variable with a ratio scale of measurement. Select one:
True
False
T
What are two ways to visually represent to measurement data variables?
- scatter plots 2. contingency tables/crosstabulation
What is a way to visually represent a mix of categorical and measurement data?
compound histogram
What is a way to visually represent categorical data pairs?
crosstabulation
What are the groupings of scores in histograms called?
bins
Do these images show the same data?
Yes
Which visual representation should you choose if you want to show that variables vary simuntaneously?
scatter-plots
What does a boxplot do?
summarises the data while showing the range, interquartile range, as well as the min, max and the median
When is the mean most useful?
best for interval/ratio measurement data (categorical data can hardly be split into 2), needs equal spacing between adjacent values
What is the mode most useful for?
all but notably for nominal/ordinal categorical data because popular choice
Variables are
properties of objects that vary in the values that they take on
A score is
an individual value for a variable
Measurement data describes
scores on a numerical scale
Categorical data describes
scores not on a numerical scale
A Population describes
a complete set of scores that might be of interest
A Sample is
a sub-set of scores from a population which were obtained