## How Big is my population?

__1: Counting Big Populations: How do scientists estimate the size of a large population?__

Scientists estimate the size of a large population by having a way to estimate the large proportion- take a random sample.

__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? _______

**97**________3: Scaling it Up: What does it mean that we scaled it up?__

We multiply the estimated number by the amount of squares on the grid

__4: Keeping it Random: Why is it important to randomly select segments to count?__

The species need an equal chance to be selected and to keep from having experimenter's bias.

__5: When Size Matters: What is the simplest way to determine the appropriate sample size?__

The simplest way to determine appropriate sample size is to graph a running average.

__6: Bare Bones Sampling: What is the difference between measuring abundance versus__

__Presence/absence?__

Abundance is the actual number of individuals given in an area. Presence/absence is when you determine many small areas to be sampled and record whether the organism was recorded or not.

__7: Collecting P/A Data: Counting Moss.. How do we estimate sample size?__

We pick points on the area and see if that point is on any moss after 10 spots, find the percentage that the point was on moss.

__8: Impervious Surface: How do we estimate impervious surface? Explain.__

We estimate impervious surface by using the presence/absence method. We pick points on the map and find out if the surface is impervious.

__9: Getting Fancy: What are the steps for conducting a simple transect?__

- Randomly select a point
- Randomly choose a direction
- Lay out a transect
- Determine where along the transect you will collect sample data
- Layout a sampling frame

__10: Try a Transect:__

__Summary: Explain wh__

__at you learned by doing this activity__

There are many different types of ways for estimating population: abundant measuring, presence/absence and transect. Abundant measuring is just counting the number of organisms in an area. Presence/absence is when you look at small areas and find if the organism was observed or not. The last way, transect is done first off by selecting a point. From that point you select a direction and lay out a transect. Find out where along the transect you will collect data, and then lay out the sampling frame.