C5

• Independent variable


  A factor that does not depend on other variable for its value
• Dependent variable


  An event or factor that is effected by, or is dependent on, other factors
• Types of data


  • Nominal
  • Ordinal
  • Interval
  • Ratio
• Nominal data


  Data that don't have numerical value, may be colors, shapes, brands, or even the number don't have value and might as well be words or letters
• Ordinal data


  Data that accommodate infinite sequences/ranks and to classify sets with certain kinds of order structures on them
• Interval data


  Data that not only provide a ranked order, but also a specific scale of measurement
• Ratio data


  Real values that can be compared to each other and are not limited to scale
• Sampling


  • Data cannot be collected on every event or object within a study area
  • The next best thing is to select or sample some of the events or object to represent all of them

  
• Statistical sampling requirements


  • A large number of samples to be representative of the population
  • Random sampling where each area has an equal chance of being selected so the sample is unbiased
  • Sample from the population or a homogenous area to which the results will be applied

  
• Sampling techniques


  • Grid tessalation
  • Grid pointing sampling

  
• Grid tessalation


  Typically used to identify a systematic pattern for determining regular or irregular sampling points, with a sample taken from each grid cell

  
• Grid pointing sampling


  The process is the same with grid tessalation, but instead of assuming that entire cell has the same nutrient value, the nutrient value is applied is applied to the point at which the sample was taken

  
• Unbiased samples


  Random sampling assures an unbiased sample

  
• Methods for assuring unbiased samples

  • Centre method
  • Offset method
  • Technique of collection sample

  
• Centre method


  Takes a sample in the center of the grid cell
• Offset method


  Creates a diamond pattern by taking the sample a certain distance offset from center
• Technique of collection sample

  Standard procedures calls for taking at least 10 samples from various location within a radius of 10 feet of the sampling point to create one composite sample

  
• Frequency


  The number of times a value occurs
• Frequency tables and graphs


  • Can help people visualize the data

  
• Descriptive statistics


  Used to describe numerically what the frequency graph or curve look like, including the center of the curve (central tendency) and the width of it (dispersion)

  
• Inferential statistics


  Used when estimating data or making an inference about differences between data sets

  
• Measures of central tendency

  • Mean
  • Median
  • Mode
• Mean


  The average of all the numbers
• Median


  The "middle" value in the list of numbers
• Mode


  The number that is repeated more often than any other
• Range


  The difference between the largest and smallest values
• Standard deviation (SD)


  Shows how much variation or dispersion exists from the average (mean), or expected value

  
• Variance


  Variance = s^2
• Correlation coefficient


  A way of measuring the relationship between paired variables
• Simple linear regression


  Tries to show that one variable is correlated to the second one
• Multivariate regression


  Uses data sets that have three or more independent attribute values to predict the dependent variable
• Most relationships are not perfectly linear
• Significance testing


  Used to determine if differences between data sets are statistically significant

  
• Research makes significant use of statistics
• The objectivity of research is based on valid data collection, the use of statistics, and the replication and control of independent variables
• A research project done once, without replication, has little validity