The document discusses the characteristics and properties of a normal probability curve. A normal probability curve is used to determine the average strength or marks of a class and how they are distributed. The key properties are that the mean, median and mode are equal and located at the center of the symmetrical unimodal curve. The curve extends from negative to positive infinity and is determined solely by its mean and standard deviation. Approximately 68%, 95%, and 99.7% of the data falls within 1, 2, and 3 standard deviations of the mean, respectively.

1. CHARACTERISTICS OF NORMAL
PROBABILITY CURVE

2. INTRODUCTION
 The literal meaning of the term normal is average.
 We make use of this term while computing the
average in data related to education , psychology or
sociology.
 In this area, those who are able to reach a particular
fixed level of qualification or characteristics are
termed as normal.
 In simple terms by probability we mean the
possibility of being selected.
 NPC is mainly computed for finding out average
strength of the class, average marks and its
distribution.

3. PROPERTIES OF NORMAL
PROBABILITY CURVE
 For this curve mean, median and mode are
the same at the centre of the curve.
 The curve is perfectly symmetrical.
 Since there is only one maximum point in the
curve, the normal curve is unimodal, i.e. it has
only one mode.

4. PROPERTIES OF NORMAL
PROBABILITY CURVE
 It extends from minus infinity to plus infinity.
 As the curve doesn’t touch the baseline , the
mean is used as the starting point for working
with normal curve.
 To find the deviation from the point of
departure(i.e. mean), standard deviation of
the distribution is used as a unit of
measurement
 There are two equal halves(50%-50%).

5. PROPERTIES OF NORMAL
PROBABILITY CURVE
 The curve extends on both sides -3 sigma
distance on the left to +3 sigma distance on the
right.
 The total area under the curve is equal to 1.
 It is completely determined by its mean and
standard deviation.
 The Empirical Rule – About 68% of the area
under the graph is within one standard deviation
of the mean; about 95% of the area under the
graph is within two standard deviations; 99.7%
of the area under the graph is within three
standard deviations of the mean.