Statistics Quiz 07 fall 2006 7.3a • Name:

  1. The figure below depicts six curves:
    Six curves
    Which, if any, of the curves in the figure above look(s) like a normal curve? If the curve is a NOT normal curve, tell why.
  2. 1. For the following curves A, B, and C determine the mean and the standard deviation σ:
    normalcurves (13K)
    CurveMean standard deviation σ
    A  
    B  
    C  

3. On the eighth of October I joggled 18 laps of the track. I had a mean lap time of = 2.5 minutes with a standard deviation of σ = 0.25 minutes. My lap times were normally distributed.

  1. p(x ≤ 2.5 minutes) = __________ What is the probability a lap had a time of 2.5 minutes or less?
  2. p(x ≤ 2.25) = __________ What is the probability that a lap was 2.25 minutes or less?
  3. __________ Of the 18 laps, how many were 2.25 minutes or less?
  4. p(x ≥ 2.67) = __________ What is the probability that a lap was 2.67 minutes or more? Use OpenOffice to answer this!
  5. p(2.33 ≤ x ≤ 2.67) = __________ What is the probability that a lap was more than 2.33 and less than 2.67? Use OpenOffice to answer this!
  6. __________How many of the laps were between 2.33 and 2.67 minutes? Use OpenOffice to answer this!

Normal Statistics
Calculate a z value from an x z = standardize.gif (905 bytes) =STANDARDIZE(x;;σ)
Calculate an x value from a zx = z σ + =z*σ+
Find a probability p(x) from a z value where the probability p is the area to the left of z. =NORMSDIST(z)

Standard normal curve with areas from -4 to +4 standard deviations.

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