data analysis Flashcards
what is the degrees of freedom calculation
df=(r-1)x(c-1)
r- rows
c- columns
what is qualitative data
non numerical data expressed in words
advantages and disadvantages of qualitative data
+ rich in detail
- difficult to analyse
what is quantitative data
numerical data
advantages and disadvantages of quantitative data
+ easier to analyse and identify patterns
- less detail
what is primary data
first hand data collected for the purpose of the investigation
what is secondary data
collected by someone other than the person conducting the research
advantages and disadvantages of primary data
+ directly relevant data= more valid
- requires more time and effort
- ethical consideration needing to be taken into account
advantages and disadvantages of secondary data
+ minimal effort and inexpensive and less time consuming
- unknown quality or relevance= less valid
what is nominal data
qualitative values usually tallied, frequency not able to rank
eg gender weather ethnicity marital status
what is ordinal data
scaled or ranked data
eg a score from 1-5
what is interval/ratio data
ranked data with equal measurement intervals
eg temperature time bank balance
what does measure of central tendency mean
a statistic that summarizes a set of data with a single value that represents the middle or center of the distribution
what does a measure of dispersion mean
the spread of data around a central value
examples of central tendency measures
mean, mode, median
examples of dispersion measures
range, standard deviation
what is standard deviation
a statistical measure that shows how spread out a set of scores are around the mean
advantages and disadvantages of using a mean
+ shows the average
+ more representative
- extreme values can cause a difference
advantages and disadvantages of using a mode
+ easier to calculate
- doesnt take into account the extreme values
advantages and disadvantages of using a median
+ unaffected by extreme values
+ easy to calculate
- doesnt take into account extreme values so less sensitive
advantages and disadvantages of using a range
+ easy to calculate
- dont know how spread out the scores are in a number set
advantages and disadvantages of using standard deviation
+ more precise
+ more accurate picture of all the data
- can be distorted by outliers
how to calculate mean
add all numbers up and divide by total amount of numbers
how to calculate mode
the most frequent value
how to calculate median
the middle number in the data after they have be ranked ordered
how to calculate range
minus the biggest number from smallest
why would you use a bar chart
for nominal data
why would you use a histogram
continuous data
(has no gaps)
what does a scatter graph show
relationship between data
what is distribution
overall pattern of data seen in a graph
how do you know its negative distribution
the mean is before the mode
how do you know its positive distribution
the mean is after the mode
what is a significance level
a measure of strength of evidence
what is teh usual significance level
p<0.05
when would psychologists use a harder significance level
when they want to challenge research
what does p<0.05 mean
95% sure the data is correct
what is a type 1 error
(false positive) reject the null hypothesis when shouldve accepted it
what is a type 2 error
(false negative) accepting a null hypothesis when shouldve rejected it
how can we remove the chances of a type 1 error
make the significance level stricter but it may increase type 2 error
how can we reduce a type 1 and 2 error
increase sample size
what is the acronym for deciding which test
carrots should come mashed with swede under roast potatoes
(chi squared sign test chi squared, mann whitney wilcoxon spearmans, unrelated t realated t pearsons)
what are the steps on finding the critical value and if it is significant
- directional or not hypothesis= one or two talied
- use the df value and find number
- use the information to see if the number should be equal or higher or lower
- if matches information then it is significant
what test is a directional hypothesis
one tailed
what test is a non directional hypothesis
two tailed
what are the steps to calculate sign test
- state alternative or null hypothesis
- represent each pair of data with + - 0
- calculate value of s (number of less frequent sign)
- look up critical value in the table using it and other pieces of data
- compare critical and calculated value and follow rule given to you
- accept/ reject hypothesis if the result is significant
What main headings should a formal write up have
Title
Abstract
Introduction
Method- design, materials, participants,procedure,ethical issues
Results
Discussion
References
Appendices
What does an abstract on a formal write up include
aim of investigation, brief explanation and hypothesis
What does an introduction in a formal write up include
Why you carried out investigation
Background knowledge on the subject
Overall aim of the study
Hypothesis type
What is included in the results section of a formal write up
Summary table and graph
Basic statistics but not explained
Justification of the statistical test used
What is included in the discussion section of a formal write up
Explanation of results
Comment on graph
Note any possible sources of error
Any corresponding modifications
What is the order that referencing information has to go in
Author
Year
Title
Edition
Place
Publisher
