Normal distribution curve is determined by:
A. Standard deviation and mean
B. Standard deviation and mode
C. Mode and median
D. Standard deviation and median
A. Standard deviation and mean
B. Standard deviation and mode
C. Mode and median
D. Standard deviation and median
Ans. A.
1. Normal
distribution curve or the Standard normal curve or Normal Gaussian curve
·A smooth
symmetrical curve.
·Total area of
the curve is 1; its mean is zero; and its standard deviation is 1.
·The mean, median
and mode all coincide.
·Limits on either
side of mean are called "confidence limits".
a) Area between one
standard deviation on either side of the mean (x±1) will include approximately
68% in the distribution.
b) The area
between two SD on either side of the mean (x±2) approximately 95 %.
c) Area between
three SD on either side of mean (x±3) approximately 99.7 % in the distribution.
• Percentage of
values in a population, which will fall within various ranges within an ideal
curve of normal distribution:
- Mean ± 1SD 68.27%
- Mean ± 1.96 SD
95.00%
- Mean ± 2SD 95.45%
- Mean ± 3SD 99.73%
2. Poisson
distribution
Limiting form of
binominal distribution when probability of success is closer to zero and
numbers of trials are infinite. Mean=variance.
3. Skew
distribution Skewed to left (negatively skewed)
• If more
outlying values are smaller than the rest, data are said to be skewed to left
·Data have longer
tail among lower values
·Median>mean -e- Skewed
to Right (Positively skewed)
• If more
outlying values are larger than the rest, data are said to be skewed to left
·Data have longer
tail among higher values
·Median<mean
