Statistics 1.5-1.11

Statistics 1.5-1.11

1. Basis concepts

   • Population: The whole
     • Sample: Part from the population
   • Qualitative Variable
     • Unmesurable things such as people characteristics
   • Quantitative variable
     • Countable things

2. Scales

   • Nominal: Identities
   • Ordinal: Identities and magnitudes
   • Interval: Identities, magnitudes and intervals
   • Ratio: Identities, magnitudes, intervals and a minimum value of 0

3. Sampling methods

   • Population parameter: True value of a population attribute
   • Sample statistic: An estimate of a population parameter
     • Probability samples
     • Non-Probability samples
       • Quotas
       • Convenience sample
       • Voluntary sample
   • Simple random sampling
     • Stratified
       • Based on certain characteristics, population is divided into groups
     • Cluster
       • Each member is randomly pointed into a group
     • Systematic
       • It has an specific order to select the members of the population
     • Multistage
       • It´s the usage of different methods

4. Visual displays of data

   • Frequency
     • It is the times an event has occurred
     • Relative frequency = F / N
   • Bar graphs
   • Circle graphs
   • Steam and leaf
   • Linear graph
   • Histogram

5. Measures of central tendency

   • Mode
     • Most repeated value
   • Median
     • Middle number in the whole list
   • Mean
     • Average

6. Measures of position

   • Z score: X-X¬/S
   • Box plot: a graph
   • Decile: D1 to D10
   • Quartile: Q1 to Q4
   • Percentile: 1% - 100%

7. Measures of dispersion

   • Standard deviation
     • ((X-X¬)/N)^1/2
     • Range
       • Amplitude between highest and lowest value
   • Coefficient of variation
     • S/X¬
   • Chevyshev´s
     • 1-1/K^2