click below
click below
Normal Size Small Size show me how
Statistics Test 1
Describing graphs, spread..etc.
| Question | Answer |
|---|---|
| When would you use a bar graph? | When you have categorical Data |
| What is important about the shape of a bar graph? | It doesn't have one with respect to skewness..etc. |
| When would you use a histogram? | Greater than 40 numbers |
| When would use use a stem-plot or a dot-plot? | Less than 40 numbers |
| What two computed values are never apart? Correlation, mean, average, median, standard deviation | Mean and Standard Deviation |
| What is the first thing you do when you see quantitative data? | Plot it. |
| What are the three properties of a histogram? | Shape, Center, and Spread |
| What is always on the x axis of a scatter-plot? | The explanatory variable |
| What is always o the y axis of a scatter-plot? | The response variable |
| What is a lurking variable? | A third variable that has a strong impact on the other vvariables, but is not measured at this time... |
| What are the three things you need to know when data is symmetric? | mean=median, bell shaped, follows 68-95-99.7 rule |
| What is the symbolic representation of Normal distribution? | N(mean, S.D.) |
| Define: Variable | Any characteristic of the objects we study |
| What are the important characteristics of a graph? | There must be space between the vertical bars, each vertical bar represents a category, the height of a bar shows the quantity in that category or the percent of total. Also, segmented bar graphs exist |
| What are stem-plots used as opposed to dot-plots? | When you want to see all the numerical data |
| Tell me about stem-plots: | They have a leaf (tens digit) and a stem (ones digit), for data you want to see, from smallest to largest, a title, four or more stems=split them |
| Define: Shape | symetric or skewed, single or multiple peaks |
| Define: Center | middle of data |
| Spread | The highest or lowest values for the main part of data? Any Outliers |
| Why is the median better than the mean? | Because it is robust to outliers |
| When would you use the mean over the median? | When the data is symetric. |
| How do you measure the spread in data? | Using an average deviation |
| What does the average deviation measure? | The distance of a value from the mean |
| What is the relationship between spread and standard deviation? | The greater the spread of data the higher the standard deviation |
| What does the five number summary consist of? | # the minimum (smallest observation)# the lower quartile or first quartile (which cuts off the lowest 25% of the data)# the median (middle value)# the upper quartile or third quartile (which cuts off the highest 25% of the data)# the maximum |
| What is association? | The relationship of two variables. Measures the form, direction, and strength (correlation) |
| When would one use scatterplots? | When there are two quantitative variables |
| What should one do looking at a scatterplot? | Look for the overall pattern, describe the pattern by form, direction, and strength, and look for outliers |
| What is the symbolic representation of the correlation? | r |
| What does correlation measure? | Measures how strong the linear relationship between two variables is. |
| What are some conditions for correlation? | It has no units, between -1 to 1, the closer the correlation to 0, the weaker the linear relationshiop |
| How many decimal placese in a mean? | 1 More Decimal place than the data |
| S.D. decimal places? | two more than data |
| Z-score | Two decimals |
| percent decimal places | At least one |
| What is the formula for a Z-score | write out |
| What is the symbol for S.D. | Mu |
| What is the symbol for mean? | Sigma |
| What is a normal distribution: | Symetric with a single peak, the distinguishing characteristics between two normal distributions are the mean and s.d. |