Presentation of quantitative data + Maths skills

Question 1

What does a bar chart represent?

Answer 1

• Type of graph in which the frequency of each variable is represented by the height of the bars

Question 2

When should bar charts be used?

Answer 2

• data is divided into categories (discrete data)

Question 3

How should data on bar charts be plotted?

Answer 3

• categories should occupy the x-axis
• the frequency/amount of each category plotted on the y-axis
• bars should be separated to denote that we are dealing with separate conditions ( categories not continuous)
• always have a title, label columns & axis

Question 4

What does a histogram represent?

Answer 4

• A type of graph which shows frequency, the area of the bars (not just height) represent frequency

Question 5

When should histograms be used?

Answer 5

• when data is continuous e.g. scores, age

Question 6

How should data on histograms be plotted?

Answer 6

• x-axis must start at 0
• x axis is made of equal sized intervals of a single category
• y axis represents the frequency within each interval
• if there is a zero frequency for one of the intervals, interval remains the same with no bar
• always have a title, label columns & axis

Question 7

What type of data is represented on a scatter graph?

Answer 7

• represents the strength & direction of the relationship between co-variables in a correlational analysis

Question 8

How should data be plotted on a scatter graph?

Answer 8

• co-variables can occupy either axis
• always have a title, label columns & axis

Question 9

What does a normal distribution represent?

Answer 9

• A symmetrical spread of frequency data that forms a bell shaped pattern

Question 10

Characteristics of a normal distribution

Answer 10

• most items are located in the middle area of the curve (very few at extreme ends)
• the mean, mode & median all occupy the same midpoint of the
  curve, highest peak (same/similar)
• tails of the curve never touch the x-axis (never reach zero)

Question 11

What is a skewed distribution?

Answer 11

• spread of frequency data that is not symmetrical, data clusters to one end

Question 12

What is a posiitve skew?

Answer 12

• a type of frequency distribution in which the long tail is on the positive (right) side of the peak & most of the distribution is concentrated on the left
• produced when scores are mostly low

Question 13

How are the measures of central tendency affected by a positive skew?

Answer 13

• The mode remains at the highest point of the peak
• median next
• mean is dragged towards tail to the right (extreme scores affect the mean)

Question 14

What is a negative skew?

Answer 14

• a type of frequency distribution in which the long tail is on the negative (left) side of the peak and most of the distribution is concentrated on the right
• produced when scores are mostly high

Question 15

How are the measures of central tendency affected by a negative skew?

Answer 15

• mode is at the highest peak
• median next
• mean pulled to towards tail left of peak (due to lower scores)

Question 16

How to work out a percentage of something?

Answer 16

• value over total number x100

Question 17

How to convert a percentage to a decimal?

Answer 17

• divide by 100

Question 18

converting a decimal to a fraction

Answer 18

• the number of decimal places equals the number of zeros it is over
  e.g.0.81 has 2 d.p.
  >8 1/100

Question 19

formula for standard form

Answer 19

(number between 1 an 10) x 10 ^ (to the power of x)

Question 20

What is a sign test?

Answer 20

• a statistical test used to analyse the difference in scores related items
• data should be nominal

Question 21

To use the sign test what should occur

Answer 21

• need to be looking for a difference
• need to have a repeated measures design
• need date that is organised into categories (nominal data)

Question 22

What is the accepted level of significance in psychology?

Answer 22

0.05 = 5%
= level at which researchers decides that the findings are significant (meaningful) & will reject the null hypothesis and accept the alternative hypothesis

Question 23

Steps for the sign test to work out calculated value

Answer 23

• work out difference between categories
• if answer is positive record + sign
  if answer is negative record - sign
• ignore if their is the same result in both categories & adjust total number of N
• add number of pluses and minuses
• take the less frequent sign & call s = calculated value

Question 24

What information is needed to locate critical value on a table?

Answer 24

• significance level (generally 0.05 or 5% unless said otherwise)
• the number of p’s in investigation (N value or sometimes degrees of freedom df)
• whether the hypothesis is directional (one-tailed) or non-directional (two tail)

Question 25

For results to be significant what does calculated value need to be?

Answer 25

• calculated value has to be EQUAL to or LOWER than the critical value for the results to be significant