analysing + interpreting data

• mode - the one that appears the most often
• median - the middle value
• the arithmetic mean - the average
• mean :

  • pros - uses all the data, most representative
  • cons - isn't always a data value, distorted by extreme values
• median :

  • pros - easy to find in ordered data, not distorted by extreme values
  • cons - isn't always a data value, not always a good representation of the data
• mode :

  • pros - easy to find in tallied data, always a data value
  • cons - doesn't always exist, might be more than one, not always a good representation
• geometric mean - used to find the mean of a set of data values that aren't immediately comparable
• the range - how far the data spreads
• standard deviation - measures spread from the mean
• for grouped frequency distibutions, x is the midpoint
• positive skew - median to the left
• negative skew - median to the right
• you can compare data sets using...

  • averages (mean, median)
  • measures of spread (range, iqr, sd)
  • skew
• retail price index - the change in price of a selection of goods and services monthly (comparing month with prev yr month)
• consumer price index - official measure of inflation but some items are excluded
• gross domestic product - the value of all the goods and services produced in a country in a given amount of time
• crude rate - how many of something happened one year per 1000 people
• standard population - 1000 people that represent the population
• capture recapture assumptions :

  • had time to mix back in
  • completely random (can't see tags)
  • unaffected by tags (not more visible by predators)
  • large enough sample size
  • tags didn't fall off