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Summary  Managerial Statistics

1 What Is Statistics

RangeLargest number  Smallest number

1.1 Key Statistical Concepts

PopulationThe group of all items of interest to a statistics practitioner.

How do you call the group of all items that are of interest to a statistics practitioner?Population

ParameterA descriptive measure of a population.

How do you call a descriptive measure of a population?Parameter

SampleA set of data drawn from the studied population.

How do you call a set of data drawn from the studied population?Sample

StatisticA descriptive measure of a sample.

How do you call a descriptive measure of a sample?Statistic

Statistical inferenceThe process of making an estimate, prediction, or decision about a population based on sample data.

How do you call the process of making an estimate, prediction, or decision about a population based on sample data?Statistical inference

Confidence levelThe proportion of times that an estimating procedure will be correct.

How do you call the proportion of times that an estimating procedure will be correct?Confidence level

Significance levelHow frequently the conclusion will be wrong.

How do you call the measure of how frequently a conclusion will be wrong?Significance level

2 Graphical Descriptive Techniques I

What is a variable?A characteristic of a population or sample

What is a value?The possible observations of a variable

What are data?The observed values of a variable

What are the 4 types of measurement levels?1. Interval (quantitative)
2. Nominal (qualitative)
3. Ordinal (qualitative)
4. Ratio (quantitative) 
What is the interval data of measurement?Real numbers, such as heights, weights, incomes, etc. Also known as quantitative or numerical data. There is an arbitrary zero point, that we as humans chose. E.g temperature. All calculations are valid, and data may be treated as ordinal or nominal.

What is the nominal level of measurement?Values are the arbitrary numbers that represent categories. E.g. man or woman Only calculations based on the frequencies or percentages of occurrence are valid. Data may not be treated as ordinal or interval.

What is the ordinal level of measurement?Values must represent the ranked order of the data. Calculations based on an ordering process are valid. Data may be treated as nominal but not as interval.

What is a frequency distribution?A categorisation of nominal values, and the counts of the categories.

What is a relative frequency distribution?Lists the values into categories and the proportion with which each occurs.

What are the 2 graphical techniques we use to describe nominal data?1. Pie chart  relative frequency
2. Bar chart  normal/absolute frequency 
What is the ratio level of measurement?The point of zero is meaningful, meaning that at 0 you really have nothing. E.g. Age, length, etc.

What are the 2 types of graphical techniques used to describe ordinal data?Also bar chart and pie chart, but the only difference is that the values at the horizontal axis of the bar chart have a logical order, as do the values in the pie chart. The pie chart is also arranged clockwise

What graphical techniques are used to describe interval and ratio data? Histograms
 Stem leaf display
 Ogive 
What is a histogram?Gives a clear summary of the set of data. Is drawn with a frequency table that counts the occurrences of a certain interval

What is the formula of Sturges?The formula that can help you decide how many intervals/classes you should have based on the number of observations. 1 + 3.3log(n), with n = the number of observations. The formula only works with more than 30 observations

What is the class width formula?(largest observation  smallest observation)/ number of classes

What are the 6 shapes a histogram can take on?1. Symmetrical  a vertical line down the middle would lead to both sides being identical in shape and size
2. Positively skewed  A peak at the beginning with a long tail extending to the right
3. Negatively skewed  Peak later in the histogram with tail extending to the left
4. Unimodal  1 peak
5. Bimodal  2 peaks
6. Bell shaped  specific histogram for normal distribution 
What is a stemleaf display?The stem is the first digit of the class, the leaf are all the second digits that fall within the class. E.g. 1 stem, 00122233 leaf

What is cumulative frequency?The frequency of the class added to the frequency of the previous class.

What is an ogive?A cumulative frequency polygon, shows the cumulative frequencies. The upper limit of the class is always displayed on the x axis, on the y axis the percentages. The highest percentage is always 100%

What are the two types of time measurements?1. Crosssectional data  measures multiple observations at the same time
2. Timeseries data  measures the same observations at different moments in time 
What is a line chart?The chart that is used to depict timeseries data. The xaxis displays the time.
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