Me, Myself and I

Question 1

what does a double mean in stats

Answer 1

describes a continuous variable

Question 2

what is a histogram

Answer 2

an accurate representation of the distribution of numerical data

Question 3

what is the median

Answer 3

the middle value - the 50% value

Question 4

what is the mean

Answer 4

the average - the sum of the collection of numbers divided by the number of numbers

Question 5

what is the mode

Answer 5

the value that occurs most frequently in a set of data

Question 6

what is the first quartile

Answer 6

middle number between the smallest number and the median of the data set. - the 25% value

Question 7

what is the second quartile

Answer 7

the median value

Question 8

what is the third quartile

Answer 8

middle number between the median and the maximum value - the 75% value

Question 9

what is a population

Answer 9

all members of a defined group

Question 10

what is a sample

Answer 10

a small subset of the population

Question 11

what is a point estimate

Answer 11

the best estimate we have - more accurate with a larger subset or a subset closer to the total population - the sample average

Question 12

give an example of a 2 sided hypothesis

Answer 12

there is a 1:1 ratio of males and females

Question 13

give an example of a 1 sided hypothesis

Answer 13

there are more females than males

Question 14

what is a one sided hypothesis

Answer 14

A one-sided hypothesis claims that a parameter is either larger or smaller than the value given by the null hypothesis.

Question 15

what is a two sided hypothesis

Answer 15

A two-sided hypothesis claims that a parameter is simply not equal to the value given by the null hypothesis – the direction does not matter.

Question 16

what is chi squared

Answer 16

where the number of observations in each class are compared to those expected under the null hypothesis

Question 17

what does a very small p value indicate

Answer 17

either that the null hypothesis is incorrect or that there is some sort of bias in the sample - we are inclined to believe that our data diverge from the null hypothesis (an alternative hypothesis may explain our data)

Question 18

what is the p value

Answer 18

the probability that we would have observed a given deviation if the null hypothesis were correct

Question 19

what are type one errors

Answer 19

false positives i.e. p = 0.049

Question 20

what are type two errors

Answer 20

false negative i.e. p = 0.051

Question 21

describe the different parts of a box plot

Answer 21

middle box - the median
lower box - lower quartile
upper box - upper quartile
whiskers - 1.5x the interquartile range or the max and min values
dots out with the whiskers - the max and min values

Question 22

what is an incidental finding

Answer 22

an observation made in the data that we were not intending to find

Question 23

what is a t test

Answer 23

determines if the mean of one group is statistically different to the mean of another group

Question 24

what is the null hypothesis

Answer 24

default expectation that there is not connection between variables (or that there is no difference between them)

Question 25

what is the 95% confidence interval

Answer 25

A 95% confidence interval has a 0.95 probability of containing the population mean. 95% of the population distribution is contained in the confidence interval. so we are 95% confident that our values lie within the defined range the range within which we are reasonably confident the population average is located

Question 26

what is a regression model

Answer 26

describes relationships between the dependent and independent variables - implies a cause and effect relationship

Question 27

what is a line of best fit

Answer 27

one line which explains the data best | all the points are as close to the line as possible - minimizing the residual space

Question 28

what are residuals

Answer 28

the difference between the observed values and those predicted by the regression line of best fit

Question 29

what is multiple r squared

Answer 29

varies from 0 - 1 - tells you the percentage accuracy of predictions based on the data

Question 30

what is adjusted r squared

Answer 30

the same as multiple r squared except it accounts for other factors and is usually lower than multiple r squared

Question 31

which statistical test provides the gradient and y intercept of data

Answer 31

t test

Question 32

what is a proptable

Answer 32

shows proportions rather than raw numbers

Question 33

if 95% confidence intervals over lap what does this mean

Answer 33

may not be a significant difference between the 2 categories - it provides insight into the robustness of any differences

Question 34

explain the difference between 95% confidence intervals in large and small samples

Answer 34

large sample - interval is narrow | small sample - interval is wide

Question 35

what is a multivariate model

Answer 35

uses multiple variables to forecast possible outcomes

Question 36

what is a fisher test

Answer 36

used when the sample size is small - when there are less than 5 data entries in a category

Question 37

what kind of condition is colour blindness

Answer 37

X linked recessive - males more likely to have it because they don't have masking by second X chromosome like females do

Question 38

what is multiple testing

Answer 38

measuring one variable against several others

Question 39

what is cherry picking

Answer 39

making something look like there is an association rather than using proper experimental design

Question 40

what is a cross sectional study

Answer 40

observational study that analyses data from a representative subset at a specific point in time uses different samples for successive observations

Question 41

what is a longitudinal study

Answer 41

involves repeated observations of the same variables over longer periods of time (can be a short timeframe too as long as observations are repeated) uses same sample for successive observations

Question 42

what does a boxplot show you

Answer 42

a visual representation of the quartiles within numeric data.