《安全工程专业英语》教学课件 unit3

Statistics for the Safety Professional
It can come from experiments in a controlled environment or from observations made. Statistics can reduce large sums of data to a manageable form, and allow the study and analysis of variance, thus allowing managers to maximize the use of information available to form an effective decision. The study and instruction of statistics can take up volumes of text. We will begin the review of statistics by describing descriptive statistics.
Mean
It can also be represented by x. The mathematic representation for calculating the mean is as follows:
=x= x1 + x2 + + xn
xn
where: µand x = average or arithmetic mean xn = individual data values
Mode
The mode of a data sample is the variable that occurs most often in the collection. For example, the mode of the sample {1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 17} is 6, since it occurs 4 times. To find the median, your numbers have to be listed in numerical order, so you may have to rewrite your list first.
Mean
The mean is also referred to as the “average” or arithmetic mean. For a data set, the mean is the sum of the observations divided by the number of observations. The mean is often quoted along with the standard deviation. The mean describes the central location of the data, and the standard deviation describes the spread. The mean is represented by the Greek letter (µ), which is mu, “pronounced moo.”
Descriptive Statistics
Descriptive statistics are just what the name implies. They are used to describe a set of data. For example, we have all heard polls on the local news that describes the data as 52% of all Americans are opposed to the latest congressional bill plus or minus 3%. What this is stating is that the range of the population that disapproves is 55% to 49%. This is a measure of central tendency.
Байду номын сангаасedian
The median is the middle value in the list of data. To find the median, your numbers have to be listed in numerical order, so you may have to rewrite your list first. If there is no “middle” number, because there are an even set of numbers, then the median is the mean (the usual average) of the middle two values. For example, given the data set {1, 2, 3, 4, 5, 6, 7, 8}, what is the median? The median would lie between 4 and 5, therefore add 4 + 5 = 9, then divide 9 by 2, giving a product of 4.5. Therefore the median for the data set is 4.5, which is the central point of the data set.
Unite Three
Statistics for the Safety Professional
Statistics are extremely important in the career of the safety professional. We utilize them to report our annual injury and accident rates, to calculate failure probability rates, and to describe observed or experimental data. For our purposes, the definition of statistics is the study of obtaining meaningful information by analyzing data. This data can come from two different sources.