Quantitative data and SPSS

In the context of data analysis, what are data best understood as?

evidence gathered to answer questions and draw conclusions

What type of variable is whether a criminal did or did not reoffend in 2 years?

Binary

What is continuous data?

• quantitative

• can be divided

• can take any value in a given range- infinate number and potential measurements

what is discrete data?

• can’t be divided

• distinct, countable, whole numbers

• quantitative

what is ordinal data?

• ordered

• qualitative

what is nominal data?

• not ordered but categorical

• qualitative

what is binary data?

• out of 2 options

what are variables (columns)?

characteristics we measure

what are observations (rows)

Individual units

what type of data is the length of a prison sentence in months? and why?

continuous- prison sentence can take any numeric value including fractions and is measured on a scale

why does ordinal data differ from categorical (nominal) data?

ordinal data has a natural, meaningful order between categories

what type of variable is a scale from 1 to 5?

ordinal

what is the most fundamental distinction when classifying types of data?

quantitative vs qualitative

if you have a choice between categorical or continuous data which should you choose and why?

continuous because you can get a lot more information

what type of data is community service hours?

discrete because it is a count of whole number hours

why does the distinction between interval and ratio scales matter when analysing continuous data?

Ratio scales have a true zero whereas interval scales do not

what is the 95% rule?

95% of the sample means fall within + or - 2 standard deviation of the mean in a normal distribution

what is the confidence interval?

a range of answers that is likely to contain the true population answer

what is standard error

describes how precisely the sample mean estimates the population mean

what is standard deviation?

describes the spread within a single sample

average distamce from the mean

what is the empirical rule?

68-95-99.7

within + or - 1 SD of all cases fall within one standard deviation of the mean

68%

within + or - 2 SD. nearly all typical cases

95%

within + or - 3 SD, virtually all data. values beyond this are outliers

99.7%

what is the population?

everyone or everything we want to make claims about

what is the sample

the subset we actually measure

what is the core problem when using data

we almost never have a population data, instead we use samples to estimate what the population looks like

what is the bell curve?

a symmetrical bell shaped curve caused by many things clustering around a centre point, with fewer cases as you move to the extremes

what does the centre of the bell curve tell us?

the mean

what does a z-score tell you?

how mnay standard deviations an observation is from the mean

what is IQR (Interquartile range) also known as?

a box plot

what is the range?

maximum - minimum

how do you calculate the IQR?

75th-25th percentile

what is the mean?

• add all the numbers together and divide by N

• the arithmetic average

what is the median?

• the middle value when sorted

what is the mode?

• the most common value

• you can have multiple modes

• identify the number that shows up the most in data

when should you use the mean?

• when data is continuous

• distribution is symmetrical

• no extreme outliers

when should you use the median?

• when distribution is skewed

• when outliers are present

• data is ordinal