Accuracy, Precision, Percent Error

Accuracy How close a measured value is to an accepted value - Accuracy can be determined by just on measurement -Depends on the quality of the measuring device The density of water is 1.00 g/mL

Precision How close a series of measurements are to one another -Precision is determined by more than one measurement -Depends on the skill of the person measuring The density of water is 1.00 g/mL

Accuracy or Precision? The boiling point of water is 100°C The atomic mass of carbon is 12 amu’s 89°C 91°C 90°C 91°C 80°C amu’s amu’s amu’s amu’s amu’s

Accuracy or Precision? The electronegativity of Fluorine is 3.8 The evaporation temperature of isopropyl alcohol is 83°C °C 89°C 90°C 89°C 90°C

Percent Error Accepted Value (also known as theoretical value) - a quantity used by general agreement of the scientific community - “what you are supposed to get” Experimental Value (also known as the actual value) - a quantitative value measured during an experiment - “what you got”

Percent Error Error = the difference between the accepted value and the experimental value Percent Error = the percent that a measured value differs from an accepted value % Error = (What you got) – (What you were supposed to get) x 100 (What you were supposed to get)

Percent Error Practice 1.The boiling point of water is 100°C. During an experiment, water came to a boil at 97°C according to the thermometer that was being used. What is the percent error of the thermometer? 2.An experiment was performed to determine the density of water. The results of the experiment showed that water had a density of 1.15 g/mL. What was the percent error in this experiment?

Qualitative Vs. Quantitative Scientists collect two different types of data: qualitative data and quantitative data. Qualitative Data: Qualitative data are descriptions in words of what is being observed. They are based on some quality of an observation, such as color, odor, or texture. Quantitative Data: Quantitative data are numeric measurements. The data are objective- they are the same no matter who measures them. They include measurements such as mass, volume, temperature, distance, concentration, time, or frequency.

Example Suppose a marine biologist observes the behavior and activities of dolphins. She identifies different dolphins within the group and observes them every day for a month. She records detailed observations about their behaviors. Some of her observations are qualitative data and some are quantitative data. Qualitative data examples  Dolphin colors range from gray to white.  Dolphins in a pod engage in play behavior.  Dolphins have smooth skin. Quantitative data examples  There are nine dolphins in this pod.  Dolphins eat the equivalent of 4-5% of their body mass each day.  The sonar frequency most often used by the dolphins is around 100kHz.