B6-B8 Statistics

Question 1

what is categorical data?

Answer 1

• value assigned indicates membership of one category
• often binary (dead or alive, yes or no)
• can be multiple outcomes
• and categories can be ordered
• ordinal data have an intrinsic order

Question 2

what are the 2 types of quantitative data?

Answer 2

discrete and continuous

they are both numerical data

Question 3

describe discrete data

Answer 3

data with known integer values
eg. number of colonies

Question 4

describe continuous data

Answer 4

numerical data with value within defined range
eg. concentrations, time

Question 5

what is a statistic?

Answer 5

measurable quantity calculated from a sample

Question 6

what is a summary statistic?

Answer 6

• a statistic used to describe / summarise a sample
• eg. mean, standard deviation, mode, variance

Question 7

what is a contingency table?

Answer 7

2-way cross-tabulation of frequencies

Question 8

what is a population?

Answer 8

• a group of all the individuals in which you are interested
• eg. cells, people, Petri dishes, molecules

Question 9

what is a sample?

Answer 9

a representative (random) sample of individuals from a population

Question 10

what is a t-test used for?

Answer 10

• looking for differences and seeing if they are statistically significant

Question 11

what are the 2 types of differences that a t-test can look for?

Answer 11

1. differences in quantitative measures among categories
2. differences in frequencies of categorical events among categories

Question 12

what is the chi-squared test used to investigate?

Answer 12

if differences between expected and observed results are statistically significant

Question 13

how does the confidence of statistical tests change with sample size?

Answer 13

larger sample = more confidence

Question 14

what are the 2 common measures of confidence?

Answer 14

• standard error of the mean
• 1.96 x SEM = 95% confidence interval