Collecting data 1
Raw data can be classed as either?
Quantitative and qualitative
what is a census
when u gather data from a whole grp
what are examples of representing data ( give 3)
two way table, pictogram, bar chart, stem and leaf, pie chart, population pyramid, choropleth etc
how to draw frequency polygon
join the midpoints of the tops of bars in a histogram.
what does standard deviation measure?
how much all the values deviate from the mean value.
advantages and disadvantages of primary data
advantages: collection method known, accuracy known, questionnaire or survey can be designed to answer specific questions.
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disadvantages: collection of data time consuming and expensive.
what is an example of random sampling?
picking a name from hat, coin flip, random number generator
what is the difference between bar charts and histogram.
bar charts are spaced out.
frequency density formula
fd + frequency/class width
what are the 3 averages?
mean median mode
what are the 3 types of experiments
field, lab and natural
what are the advantages of random sampling?
more likely to represent the population,
unbaised
in a stem and leaf diagram, which one must be single digit
the leaves
in a positive skew, where most of the data
lower end
Q1 - 1.5 x IQR
Q3 + 1.5 x IQR
what is the advantage of a laboratory experiment?
easy to replicate, can control extraneous variables.
list an example of non random sampling
judgement, opportunity, cluster, quota, systematic
R2 /r2 = N/n
3d diagram/ 3d bar chart
where does the median lie in a positive skew in a box plot.
Towards the left hand end
how do we clean a data?
identity and correct or remove inaccurate data/outliers.
check units are consistent
record values without symbols or units
stratified sampling formula
stratum size/ population size x number in sample
how do chloropleth maps show data
using different colours and shades.
why are 3d bar charts misleading?
it is difficult to distinguish between heights of bars.
what is the advantage and disadvantages of mean
advantage: uses all the data, can be used to find skew or s.d
disadvantage: afftected by extreme values,