Categorizing Data
The values of this type of variable are typically recorded as text, as they have no numerical value
What is qualitative data?
Descriptive statistics give us a sense of (a) the ___ of the data and (b) the ___ of the data across the spectrum of values.
a) location b) spread
note: What do each of these mean?
This plot type is useful for exploring the relationship between a discrete dependent variable (y) and a qualitative independent variable (x)
What is a barplot?
What is the term for making inferences from our data about patterns and processes exhibited by a larger group of organisms?
Inferential statistics
When do we use a non-parametric test?
If the data are not normally distributed
These variables are quantitative; they still measure an
amount. Yet, they are limited to certain values, such as whole numbers.
What are discrete variables?
What is the pattern of a normally distributed data set?
Bell shaped curve
This plot type is useful for visualizing the relationship between a continuous dependent variable (y) and a qualitative independent variable (x)
What is a boxplot?
Results with p-values less than or equal to this value are called “statistically significant.”
p<0.05
Name two questions you should ask when determining the appropriate statistical test for your data
1) Is the dependent variable qualitative or quantitative?
2) Does the data for the dependent variable follow a normal distribution?
3) Is the independent variable qualitative or quantitative?
4) If the independent variable is qualitative, how many levels are there?
This is X, the variable potentially influencing
our variable (Y) in a hypothesis test
Independent Variable
This value helps quantify how accurately you
have measured the true mean of the whole population by obtaining the mean of a smaller sample
Standard error of the mean
This plot type explores the relationship between two quantitative variables (continuous or discrete)
What is a scatterplot?
True or false: The lower the variation in your data, the more confidence you can have that observed differences are from your treatment and not from other factors.
True
Name the appropriate test for this data: Is there a difference in dune plant height between 5 species?
ANOVA
Name the data type: sampling location, presence/absence data, habitat type
Nominal data
How do we assess the distribution of data (hint: it's a plot type)?
By constructing histograms, whereby the values of the data are on the x-axis and the frequency of those values that are in the dataset is on the y-axis
Name the appropriate plot for this data: distance in meters from the shore (x) vs mole crab length (y)
scatterplot (two quantitative variables)
What would be the R2 value if our data fit perfectly to the model (for example, if all the data points fell exactly on the regression line)
R2=1
Name the appropriate test for this data: Does the number of plankton species differ between the Santa Monica and Venice piers?
independent t-test
ALL GROUPS
Name the independent and dependent variables and the data types collected for this study: Scientists collected snowy plover body weight and # of chicks in protected vs unprotected nesting sites
Independent: Protected vs unprotected sites
Dependent: body weight, # of chicks
Body weight: continuous
# of chicks: discrete
How do we calculate standard deviation?
By adding the squared deviations of each sample value from the mean, dividing by the sample size, and taking the square root
Name the appropriate plot for this data: tide pool location (x) vs number of species (y)
barplot
What does the p-value of our data tell us?
The p-value helps evaluate how likely it is that the observed differences between treatment and control (or other factors being evaluated) would occur if in reality, the treatment had no effect.
Name the appropriate test for this data: Does the size class of mussels affect the presence of drill holes from whelk predation? Bonus: what type of data are each of these variables?
Chi-square test, categorical