Frequency Distributions

Frequency Distributions

Standard Deviation

According to (Lyman & Michael, 2010) Standard deviation is a statistical technique used to measure the dispersion of data from its mean value or deviation of data. The high value of standard deviations refers to high deviation from its mean value and vice versa (Anderson et al, 2008). Furthermore, standard deviation also measures of how accurate the average is, means that how the numbers independently agree with one another. This technique measure a type of error known as random error. This is a type of error which cannot be controlled by the people .

Normal Distribution

Normal Distribution explains the continuous data which possess a symmetric distribution and having a feature of “bell” shape (Frederick & Larry, 2009). This is the most commonly used distribution in statistics. The reason is that the normal distribution approximates various natural phenomena very well. It also has developed into a standard's reference for multiple problems related to probability.

The data set which has normal distribution must have equal values of mean, median and mode like mean= median= mode. In addition to this the symmetry in normal distribution fall about the centre which refers that 50% of values lie less than the mean and 50% greater the mean. The above diagram represents the bell shaped curve of normal distribution.

Data of different prices quoted by eight appliances stores are given in table 1.

Appliance Stores

Price of CD model

1

$218

2

$125

3

$381

4

$187

5

$231

6

$213

7

$309

8

$230

Table 1

The standard deviation of the data is presented in table 2.

Descriptive Statistics

N

Minimum

Maximum

Mean

Std. Deviation

Price

8

125.00

381.00

236.7500

77.44629

Valid N (listwise)

8

Table 2

Graph 1

The above graph shows that the data of price of CD model is not normally distributed as the graph is not a bell shaped curve.

The investigated time required for drive through service of Wendy's and McDonalds is presented in table 3.

Time in Seconds

No of Observations

Wendy's

McDonalds

1

110

105

2

113

116

3

133

131

4

198

176

5

124

118

6

120

110

7

154

135

8

110

137

Table 3

Results

The results of two groups are presented in ...