What is statistics?
a branch of mathematics that provides techniques to analyze whether or not your data is significant (meaningful)
Statistical applications are based on probability statements
Nothing is “proved” with statistics
Statistics are reported
Statistics report the probability that similar results would occur if you repeated the experiment
Statistics deals with numbers
Need to know nature of numbers collected
Continuous variables: type of numbers associated with measuring or weighing; any value in a continuous interval of measurement.
Examples:
Weight of students, height of plants, time to flowering
Discrete variables: type of numbers that are counted or categorical
Examples:
Numbers of boys, girls, insects, plants
Populations and Samples
Population includes all members of a group
Example: all 9th grade students in America
Number of 9th grade students at SR
No absolute number
Sample
Used to make inferences about large populations
Samples are a selection of the population
Example: 6th period Accelerated Biology
Why the need for statistics?
Statistics are used to describe sample populations as estimators of the corresponding population
Many times, finding complete information about a population is costly and time consuming. We can use samples to represent a population.
Sample Populations avoiding Bias
Individuals in a sample population
Must be a fair representation of the entire pop.
Therefore sample members must be randomly selected (to avoid bias)
Example: if you were looking at strength in students: picking students from the football team would NOT be random
Mode and Median
Mode: most frequently seen value (if no numbers repeat then the mode = 0)
Median: the middle number
If you have an odd number of data then the median is the value in the middle of the set
If you have an even number of data then the median is the average between the two middle values in the set.
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