Statistics Midyear Final
Terms
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- What is statistics?
- the science of learning from data
- Why is anecdotal evidence not considered valid statistical data?
- Valid statistical data describes the overall picture rather than focusing on a few incidents.
- Describe the advantages of using available data. Identify at least two methods of obtaining it.
- Available data is not as expensive as new data. Two sources are the library and internet.
- Identify the three main statistical designs for producing data.
- Surveys, observational studies, and experiments.
- Describe the characteristics of a survey.
- Select sample of random people to reprisent a larger population. Ask a question and draw conclusions.
- Describe the characteristics of an observational study.
- Select a sample to reprisent a population. Observing and measuring (no interference) the variable. Do not attempt to influence the response.
- Describe the characteristics of an experiment.
- Goal is to understand cause and effect. Deliberately do something to individuals to observe responses.
- Differentiate between categorical and quantitative variables.
- Catergorical variables records to which of several groups an individual belongs whereas quantitative takes numerical values for which arithmetic operations make sense.
- Explain exploratory data analysis.
- This is the examination of data using graphs or numerical studies.
- Define the distribution of a variable.
- Tells us what values the variable take on and how often each value occurs.
- What is an outlier?
- An observation that falls outside the overall pattern.
- What is the center?
- The value that divides the observation in half.
- What is the spread?
- The smallest to the largest piece of data (ignoring outliers).
- What are the 4 shapes of a distribution of data?
- Symmetric, skewed right, skewed left, uniform.
- What is the interquartile range (IQR)?
- The distance between the 1st and 3rd quartile. IQR = Q3 - Q1
- What is the 1.5(IQR) rule?
- This determines if an observation is an outlier. It is an outlier if it falls more than 1.5(IQR) above the 3rd quartile or belows the 1st quartile.
- Is the mean resistant to outliers? Explain.
- The mean is nonresistant because it is sensitive to the influence of extreme outliers.
- Is the median resistant to outliers?
- The median is resistant to outliers.
- What is the midrange and how is it calculated?
- This is the value midway between the highest and lowest scores. midrange = (high + low)/2
- When data is transformed, how are center and standard deviation effected?
- When x(new)= a + bx, the center is effected by both a (added) and b (multiplied), while standard deviation is only effect by b (multiplied).
- What are the properties of a density curve?
- It is always on or above the horizontal axis and it has an area of exactly 1 under it.
- What is the equation of the z-score?
- z = (x - μ)/(σ) or z = (x - mean)/(standard deviation)
- What are the percentages of a normal distribution? (Empirical Rule)
- 68-95-99.7
- What should the overall pattern of a scatterplot reveal about the relationship between the 2 variables?
- Should reveal the direction, form and strength of the relationship and should also determine if there are any outliers.
- Explain the 2 types of direction when viewing a scatterplot.
- Positively Associated- upward slope Negatively Associated- downward slope