1: Counting Big Populations: How do scientists estimate the size of a large population?
Scientists take a random sample to determine the size of a population
2: Sampling on a grid: To count the dandelions, we'll first create a grid, then use the computer's random number generator to tell us which grid squares to count. We'll do this 10 times, because, as you'll see, the counts in the different grid squares will vary a lot. After you count 10 squares, you'll use the average number per square to estimate the population of the entire lawn. How many dandelions are there on the grid? 92
3: Scaling it Up: What does it mean that we scaled it up?
To take a smaller segment of an area and using that as a proportion to measure the the entire area
4: Keeping it Random: Why is it important to randomly select segments to count?
It is important to keep it random to prevent experimenter's bias. Experimenter's bias is when the experimenter has a tendency to choose:
The simplest way to determine the appropriate sample size is to graph a running average
6: Bare Bones Sampling: What is the difference between measuring abundance versus Presence/absence?
Abundance: The quantities of individuals found in a given area
Presence/Absence: Determining small areas or points and seeing if an organism was observed or not
7: Collecting P/A Data: Counting Moss.. How do we estimate sample size?
You can estimate sample size by picking random individual points
8: Impervious Surface: How do we estimate impervious surface? Explain.
You can measure impervious surface by using the P/A method. You would pick random points in an area and determine how many of them have an impervious surface
9: Getting Fancy: What are the steps for conducting a simple transect?
10: Try a Transect:
Scientists take a random sample to determine the size of a population
2: Sampling on a grid: To count the dandelions, we'll first create a grid, then use the computer's random number generator to tell us which grid squares to count. We'll do this 10 times, because, as you'll see, the counts in the different grid squares will vary a lot. After you count 10 squares, you'll use the average number per square to estimate the population of the entire lawn. How many dandelions are there on the grid? 92
3: Scaling it Up: What does it mean that we scaled it up?
To take a smaller segment of an area and using that as a proportion to measure the the entire area
4: Keeping it Random: Why is it important to randomly select segments to count?
It is important to keep it random to prevent experimenter's bias. Experimenter's bias is when the experimenter has a tendency to choose:
- The most convenient sample
- The fullest segment
- Least full segment
- The most interesting segment
The simplest way to determine the appropriate sample size is to graph a running average
6: Bare Bones Sampling: What is the difference between measuring abundance versus Presence/absence?
Abundance: The quantities of individuals found in a given area
Presence/Absence: Determining small areas or points and seeing if an organism was observed or not
7: Collecting P/A Data: Counting Moss.. How do we estimate sample size?
You can estimate sample size by picking random individual points
8: Impervious Surface: How do we estimate impervious surface? Explain.
You can measure impervious surface by using the P/A method. You would pick random points in an area and determine how many of them have an impervious surface
9: Getting Fancy: What are the steps for conducting a simple transect?
- Randomly select a starting point in your area of interest
- Determine a random direction from the starting point
- Lay out a transect to create a path from the starting point to the random selection. Length is up to you
- Determine where along the transect that you will collect your data
- Layout an outline of where you are sampling on the transect
10: Try a Transect:
Summary: Explain what you learned from doing this activity
From this activity I learned different methods of estimating population. One of the method is called abundant measuring. This method is when you count individuals in a given area. Another method is known as presence/absence. This method is determining small points in the entire ecosystem and seeing if an organism was observed or not. The last way of estimating population is using a transect. This method has five steps and it involves somewhat strategically placed "frames" for measuring populations
From this activity I learned different methods of estimating population. One of the method is called abundant measuring. This method is when you count individuals in a given area. Another method is known as presence/absence. This method is determining small points in the entire ecosystem and seeing if an organism was observed or not. The last way of estimating population is using a transect. This method has five steps and it involves somewhat strategically placed "frames" for measuring populations