Correlations and descriptive stats. Flashcards
What is a scattergram?
A type of graph that represents the strength and direction of a relationship between co-variables in a correlational analysis.
What is a correlation?
Demonstrates a relationship between two variables on a scattergram.
What is the difference between an experiment and a correlation?
-Experiments manipulate the IV to measure the effect on the DV, in order to establish a cause for the difference in DV.
-Correlations just state a relationship but does not say one causes another.
How to tell the strength of a correlation?
How close the points are to the line of best fit.
What are correlation coefficients?
Measures the strength and direction of a linear relationship between two variables on a scatter plot.
-Closer to -1 strongest negative.
-Closer to 1 strongest positive.
Advantages of correlations?
-quick and economical to carry out
no need for controlled environment/ manipulation of Vs
can be used when its unethical to manipulate Vs to see if one V affects the other
-if a relationship is found, then it can justify other research
Disadvantages of correlations?
-Can not tell cause and effect!
-May have the third variable problem.
-Can be misused and misinterpreted by the media.
What is qualitative data?
Expressed in words (written descriptions, thoughts feelings from interviews or open questions).
-Greater external validity.
-Difficult to analyse.
What is quantitative data?
numerical data
-From closed questionnaires, experiments.
-Simple to analyse.
-lacks detail and external validity.
What is primary data?
Data collected by the researcher FOR THE SPECIFIC PURPOSE OF THE RESEARCHER.
-Authentic and up to date.
-More time and effort.
What is a meta analysis?
-The results from a number of studies investigating the same hypothesis are identified and reviewed, to produce a joint conclusion.
What is secondary data?
information that already exists somewhere, having been collected for another purpose.
-easy to access and inexpensive.
-may not fit the investigation.
Advantages of meta analysis?
It creates a larger more valid sample because it can be generalised more.
Limitations of meta-analysis?
- inclusion of poorly conducted studies in equation
- cost of conducting the study
- criteria being used for including primary sources are difficult to agree upon
- incomplete data sets
- publication bias as researcher may not use studies that contradict the hypothesis.
What is a measure of central tendency?
finding the most typical value in the data.
Mean:
Obtained by adding the scores and then dividing by the number of scores.
-Sensitive and extreme values will distort it.
Median:
Order the data and is the middle number.
-Not affected by extreme values but less sensitive than the mean.M
Mode:
The most common value.
-Easy to calculate but most of the time does not represent the data well.
-Good more categoric data.
What are measures of dispersion?
Measurements of the spread of scores within a set of data and include the range, standard deviation and variance.
Range:
the difference between the highest and lowest scores in a distribution.
-1 is often added because results in the data are often rounded, so this accounts for the margin of error.
-Easy to calculate.
-Extreme values distort.
Standard deviation:
a computed measure of how much scores vary around the mean score.
-More precise than the range.
-Harder to calculate and can be distorted.
What does a larger/smaller standard deviation mean?
Data is more spread out/data is more concentrated around the mean value.
What is a normal distribution?
A “normal” distribution is also known as a bell-shaped curve or Gaussian curve. In a Gaussian or normal distribution, the mean , mode and median would all have the same (or similar) value and would look like the figure.
What is a positively skewed distribution?
A distribution where the right tail (end) of the distribution is pulled further than the left tail. A distribution where there are more extreme high scores than low scores.
-The mean is more than the mode and median
RIGHT FOOT.
What is a negatively skewed distribution?
A distribution where the left tail (end) of the distribution is pulled further than the right tail. A distribution where there are more extreme low scores than high scores.
-Mean is less than the mode and median.
LEFT FOOT.
What is a bar chart?
A type of graph in which the frequency of each variable is represented by the height of the bars. Discrete data
What is a histogram?
a diagram consisting of rectangles whose area is proportional to the frequency of a variable and whose width is equal to the class interval. Continuous data.
