Question. Dinner at the Urquhart House. Data, Statistics, and Spreadsheets. Data. Types of Data. Statistics and Data

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1 Question What are data and what do they mean to a scientist? Dinner at the Urquhart House Brought to you by the Briggs Multiracial Alliance Sunday night All food provided (probably Chinese) Contact Mimi Reddy, reddydee@msu.edu for details Data, Statistics, and Spreadsheets What are data? What are statistics? What are spreadsheets? How can you analyze data with spreadsheets? Data Data are pieces of information Data can be numbers, words, descriptions Data have UNITS The word data is PLURAL, datum is singular Data about Willoughby: Age: 5 (years) Height: 47 (inches) Weight: 66 (pounds) Eyes: Blue Favorite word: Wrestle Favorite letter: W Types of Data Statistics and Data Numbers two types Real #s rational numbers lbs Integers whole numbers 18 months Letters called characters in programming W is a character Words called strings in programming No thanks is a strings, can be individual words or phrases Test Scores: Jeff: 88 Mollie: 92 Marcie: 88 Dave: 47 Karim: 99 Willoughby: 42 Benjamin: 0 What statistics can you calculate to describe these data? Try to think of four things to describe the data stop

2 Statistics Statistics are derived from the data Statistics are descriptions of data Statistics are meant to simplify the data Statistics can be misleading Typical Statistics Sample Size - number of individuals measured = n Sum = Σ Average or Mean = Σ/n Median Value of 50th percentile, half of values fall above, half below Maximum, Minimum, Range (Max-Min) Mode - most common value Standard deviation Variance (SD 2 ) Analyze these data... Mean, max, min, range, median, mode sample size (n) Sum Σ mean=average=σ/n denoted x median = halfway mode = most common Spreadsheets Spreadsheets are tables CostaRica Nicaragua Rainforest 625,000 3,712,000 Dry Forest 50, ,000 Total 675,000 4,012,000 Spreadsheets allow calculations and manipulations of data Calculations: mean, standard deviation Manipulations: sort, Make a data table: Data Table Fly 1, length 13.4 mm, velocity 27 Kph, age 21 days Fly 2, length 9.4 mm, velocity 0 Kph, age 220 days Fly 3, length 9.3 mm, velocity 44 Kph, age 1 days Fly 4, length 13.4 mm, velocity 17 Kph, age 32 days Fly 5, length 17.4 mm, velocity 33 Kph, age 11 days Fly # 1 2 Length Velocity Age How many columns? How many rows? #s go down or across? 3 4 5

3 Microsoft Excel Typical spreadsheet program Lotus is original commercial spreadsheet Has similar controls to MS Word Now allows graphing (charts) very restricted formats, hard to get exactly what you want Excel tables and graphs can be copied into MS Word Friday s Assignment We will work with Microsoft Excel to analyze some data Groups of two will submit one finished spreadsheet for the assignment Graphs Many different types of graphs Points Lines Bars Pies Point Graphs Called X-Y Scatter in MS Excel Plot points based on X and Y value Can fit a REGRESSION LINE to the data Line that best fits the data X-Y Scatter Bar Graphs Categorize data into counts or percents Categories can be descriptive categories (Windows 98, Windows 2000, ) Can also be numeric categories Height: 60-63, 63-66, etc. or just 61, 62, 63 Count up number of people in each group Histograms are a particular type of bar graph

4 Bar Graph Histogram $50,000 $40,000 X axis is categories Y axis is a number or proportion of observations in that category $30,000 $20,000 $10,000 $ Histogram Bar Graph Regular Bar Graph vs. Histogram Bar Graph Number of Crashes $50,000 $40,000 $30,000 $20,000 $10,000 $ Distributions Sample distribution histograms Special type of histogram with continuous numeric scale at bottom Normal distribution is a key concept in statistics Skewed distribution is one that is unbalanced Danyoungyoo, Katanchalee, and Srichawla, Robert D. Duval, PS 400 Lecture,

5 The NORMAL Distribution A NORMAL DISTRIBUTION is the theoretical distribution of values given natural variation around a MEAN It is balanced, humped distribution Distributions Skew is an imbalance in the distribution Danyoungyoo, Katanchalee, and Srichawla, Hypothesis Testing Statistical Tests are how scientists decide if data support their hypothesis (NOT PROVE their hypothesis) Four major statistical tests: T-test, X2 Test, Regression, ANOVA Hypothesis Processor speed has an effect on the performance of the computer. Null Hypothesis H 0 : Processor speed has NO EFFECT on the performance of a computer. Statistical Tests and Probability Statistical tests give a value That value can be related to a probability Probability is likelihood that NULL hypothesis is correct given the data you have If P < 0.05 (1/20), then you conclude NULL hypothesis is FALSE T-Test Compares differences between two means Formula: T = (x 1 -x 2 )/SEM SEM is Standard Error of Mean [SD/(N-1)] T Values: Difference between mean in comparison to the amount of spread in your data

6 T-Values If T > 2.5 or 3.0, difference is usually significant (this depends on your sample sizes)