construction engineering 221 probability and statistics

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Construction Engineering 221 Probability and statistics

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Page 1: Construction Engineering 221 Probability and statistics

Construction Engineering 221

Probability and statistics

Page 2: Construction Engineering 221 Probability and statistics

Data description

• Random sample- every member of the population has an equal chance of being selected into the sample. Hard to do (unlisted phone #’s, no permanent address)

• Can use random number generator

• Non-random is OK if biases are known and reported

Page 3: Construction Engineering 221 Probability and statistics

Data description

• Data from the sample represent an array (rows and columns) in raw form- how it might look on an Excel spreadsheet

• Can organize the data in various ways to simple the array and make it more “readable”– Classification- like letter grades, use class

intervals to combine similar scores

Page 4: Construction Engineering 221 Probability and statistics

Data description

– Class boundaries separate one class from another

– Edges of boundaries are “class limits”, and represent the data where most information is “lost”

– Class size, interval, and boundary are arbitrary– Class mark is the midpoint of the class limits

Page 5: Construction Engineering 221 Probability and statistics

Data description

• Class frequencies are the number of scores within each class

• The list of frequencies forms a distribution that typically assumes one of several standard forms (Normal, Chi Square, Poisson, Binomial)

• Cumulative distribution is a representation of number of scores below. When divided by total, the number represents a percentile rank

Page 6: Construction Engineering 221 Probability and statistics

Data description

• Histogram is a common graphical representation of a frequency distribution

• Frequency polygon connects the midpoints of the histogram class limits and represents data distribution as a line

• Ogive- cumulative distributions- normal distribution will have an S-shaped ogive

Page 7: Construction Engineering 221 Probability and statistics

Data description• Common engineering distributions

WeibullPoissonPower log normal

Binomial Chi square Log normal Normal