unit 0

Question 1

controlled experiment

Answer 1

a scientific test done under controlled conditions: meaning that just one (or a few) factors are changed at a time, while all others are kept constant

Question 2

what are the components in a controlled experiment?

Answer 2

independent variable
dependent variable
control group(s)
experimental group(s)
constants (also called “control variables” or “controls”)

Question 3

before the experiment, what are the steps you need to take?

Answer 3

1. make an observation
2. make a scientific question
3. create a hypothesis
4. develop a controlled experiment alongside the hypothesis to test if it is correct or not
5. do research in order to develop a good, educated hypothesis and to begin finding ideas for how to best test the hypothesis

Question 4

what is a hypothesis?

Answer 4

a testable prediction that addresses the question (a “best guess”)

Question 5

define “independent variable”

Answer 5

this is the variable (factor) that the experimenter controls and changes between the different groups being tested

Question 6

define “dependent variable”

Answer 6

this is the variable that is predicted to change in response to the independent variable. it depends on the independent variable, not vice versa

Question 7

define “constants/controls”

Answer 7

these are all the other variables that are kept identical between all the groups being tested

Question 8

define “experimental group”

Answer 8

the groups that receive some version of the independent variable

Question 9

define “control groups”

Answer 9

the group that does not receive the independent variable. this group provides a baseline that lets the experimenter see if the independent variable has an effect

Question 10

define “negative control group”

Answer 10

DO NOT receive any additional treatment that is expected to have an effect. they are identical to the experimental groups, except they do not receive the independent variable

Question 11

define “positive control group”

Answer 11

DO receive an additional treatment that is known to produce the effect expected in the experimental groups. they are identical to the experimental groups, except they: (1) do not receive the independent variable and (2) receive some other treatment/variable that is different than all the other groups

Question 12

characteristics of a strong hypothesis?

Answer 12

should be TESTABLE, include the INDEPENDENT & DEPENDENT VARIABLES, and make a SPECIFIC PREDICTION about the outcome of an experiment
using an “if-then” statement helps to make sure a hypothesis meets these expectations, but it is not required

Question 13

what are data tables?

Answer 13

constructed to record and organize important data collected during an experiment

Question 14

what are graphs?

Answer 14

allows scientists to more easily identify patterns or trends between variables

Question 15

types of graphs often used in AP bio?

Answer 15

bar graphs, histograms, box & whisker plots, scatter plots, line graphs, & pie charts

Question 16

define “bar graphs”

Answer 16

; used when data can be divided into categorical groups (e.g. sex, grade level, # of siblings, favorite type of movie, groupings of time, etc)
; represents categories on one axis and a measured value on the other
; can be vertical or horizontal

Question 17

define “histograms”

Answer 17

; show the distribution, or frequency, of outcomes
; “count” the occurrence of outcomes that fall into divided ranges for a certain continuous variable being measured
; one axis contains the ranges, and the other represents the frequency or number of data points that fall into each range
)all bars touch

Question 18

define “continuous variables”

Answer 18

contain values that are not discrete or categorical, but exist along a spectrum
e.g. score on a test, temperature, time, height, age, etc.

Question 19

define “box and whisker plots”

Answer 19

; used to show the distribution of data points, but in a more summarized way
; display the “five-number summary” of the data set
; includes maximum value, minimum value, lower quartile, median, and upper quartile

Question 20

define “scatter plots”

Answer 20

; used to show the overall relationship between two variables, if one exists
; both axes plot a continuous variable being measured
; measurements of the independent variable are plotted on the x-axis, while measurements of the dependent variable are plotted on the y-axis

Question 21

define “line of best fit”

Answer 21

drawn through the average of the points in order to show a trend that might exist between the two variables

Question 22

define “line graphs”

Answer 22

; used to show the relationship between two continuous variables
; typically are used to track changes over time, x-axis usually represents time & y-axis usually represents another variable that is being measured over a certain course of time
; chosen over scatter graphs only when it becomes important to see the individual changes that take place from point to point, instead of an overall relationship

Question 23

define “pie charts”

Answer 23

used to compare categorical groups proportionally with one another

Question 24

define “standard error of the mean”

Answer 24

; common form of statistical analysis used in biology experiments. it is used to measure how much the data taken from a sample group deviates from the actual population

Question 25

what does it mean when the SEM is high?

Answer 25

the data taken from the sample group does not very accurately represent the entire population, there was a lot of variation in the data collected from the sample group

Question 26

what does it mean when the SEM is low?

Answer 26

the data taken from the sample group more accurately represents the entire population, there was little variation in the data collected from the sample group

Question 27

statistical significance

Answer 27

averages of the two groups with plus or minus two SEM should NOT overlap

Question 28

define "error bars"

Answer 28

created using plus or minus 2 SEM, which gives 95% certainty that the difference between two groups is real and not due to chance (if they do not overlap)

Question 29

define "chi-squared test"

Answer 29

another common form of statistical analysis used in biology, also called a "goodness-of-fit" test, used to determine if the observed distribution of a given phenomenon is significantly different from an expected distribution

Question 30

define "null hypothesis"

Answer 30

states that the data will be consistent with a specific, expected distribution (usually the distribution that results from random chance or some other predetermined expectation), and it typically specifies the proportion to be found in each category

Question 31

define "alternative hypothesis"

Answer 31

predicts an outcome that does not match the expected distribution

Question 32

if chi-squared value exceeds the critical value for a p-value of 0.05?

Answer 32

reject the null hypothesis

Question 33

if the chi-squared value is less than the critical value for a p-value of 0.05?

Answer 33

accept the null hypothesis