Probability

Question 1

Define:

• Probability

- Conditional probability

Answer 1

• Refers to likelihood of a particular event happening

- Probability of an event happening even if another event has also happened

Question 2

Describe normal distribution

Answer 2

• Symmetrical
• Tails should meet at x axis indefinitely
• Should be bell shaped
• Same number for mean, median, mode
• Negative skew is shifted towards high numbers
• Positive skew is shifted towards low numbers

Question 3

Describe kurtosis

Answer 3

• How peaked or flat the distribution is
• Highly peaked = leptokurtic
• Flat = playkurtic
• Middle (near 0) = mesokurtic

Question 4

Describe z scores

Answer 4

• Raw score - mean = mean deviation

- Mean deviation/standard deviation = z score

Question 5

Describe confidence intervals

Answer 5

• Important to get representative samples when collecting data from a population (the larger the sample, the more accurate)
• Need to know how much our sample reflects the population
• Expressed as one score below and one score above the mean
• Usually use 95% confidence intervals
• The smaller the sample size, the greater the confidence interval will be
• They allow us to compare scores on 2 samples; if confidence levels overlap, it is likely the population means is the same and there is no significant difference between them

Question 6

Describe error bars

Answer 6

• Can be used to plot confidence intervals for each mean to explore the difference between the 2 means
• Confidence intervals provide us with a probability that the mean value of the population from which the sample was drawn falls within a particular range
• Can use error bars to explore differences between 2 means before carrying out inferential statistics