In sheet ‘STATS’ row 26 I calculate the skew for various small samples. Our sample of 30000 gave us a skew of 0.00561 Closer to zero means more symmetrical. If a data-set is perfectly symmetrical (left side of chart is exactly like right side) the skew is zero.
If we traveled to The Netherlands my standard deviation would be 1.7 and Bill’s would be 0.6. Bill would be 3.4 standard deviations above the mean. Of course not but we’d be perceived as being taller by the local people! In Bolivia my height would put me 4.5 standard deviations above the 5 feet 3 inch mean (2.92 inch SD). What if Bill and I were to travel to Bolivia? Would we be taller? This entire post I’ve been referring to male height in the United States. Kevin Durant is 6 feet 11 inches with a standard deviation of 4.7 Men above 6 feet 6 inches (past 3rd standard deviation) are extremely tall. My 2.38 standard deviation is between the 2nd & 3rd deviation above the mean.
Measures the spread of the numbers from the average (mean) in normally distributed data-sets. Normal distribution is also known as Gaussian distribution and the bell curve. Values may cluster around the mean or be more spread out. Normally distributed data-sets share this symmetry but the spread varies. Left and right sides of the chart are symmetric. average male height is 5 feet 9.3 inches (69.3 inches, 176 cm). Some are taller (to the right) or shorter (to the left). and test scores have in common? All are normally distributed.Ĭhart below shows: most are close to the mean(average), half are above the mean and half are below. Instead of using adjectives to describe our height we’ll use standard deviations. Internally you do the math.īill is 6 feet 1 inch (185 cm). In a crowd you compare the height of those around you. It’s easier to visualize than test scores or IQ. Normal Distribution & Standard Deviation allow us to compare height. Tim is 2 meters tall! That’s extremely tall!.How do we compare these numbers to others? Numbers describe height, intelligence and tests. We’ll review the concepts and use Excel to crunch the numbers. How tall is tall? How smart is smart? How do we compare? Normal Distribution and Standard Deviation answer this.