A measurement system is valid if it is both "accurate" and "precise". Related terms include "bias" (non-random or directed effects caused by a factor or factors unrelated to the independent variable) and "error" (random variability).
The terminology is also applied to indirect measurements—that is, values obtained by a computational procedure from observed data.
In addition to accuracy and precision, measurements may also have a measurement resolution, which is the smallest change in the underlying physical quantity that produces a response in the measurement.
The word "precision" also refers to how fine the measurement is made, as the "resolution" of the measurement, such as to the nearest meter, centimeter, or yard, foot, inch, or nanometer.
In the case of full reproducibility, such as when rounding a number to a representable floating point number, the word "precision" has a meaning not related to reproducibility. For example, in the IEEE 754-2008 standard, it means the number of bits in the significand (number of digits in the amount), so it is used as a measure for the relative accuracy with which a number can be shown.
Humidex
The humidex ("Hyu-mah-deks") is a temperature index used by Canadian meteorologists to describe how hot the weather feels to a person, by adding the effect of heat and humidity. For example, if the temperature is and the calculated humidex is 40, then that means the humid heat feels like a dry temperature of . The index is widely used in Canadian weather reports during summer to give the discomfort level.
According to the Meteorological Service of Canada, a humidex of at least 30 causes "some discomfort", at least 40 causes "great discomfort" and above 45 is "dangerous". When the humidex hits 54, then heat stroke is very near.
The current formula for getting the humidex (see below: Humidex formula) was developed by J.M. Masterton and F.A. Richardson of Canada's Atmospheric Environment Service in 1979. The humidex differs from the heat index used in the United States, in being derived from the dew point rather than the relative humidity.
The record highest humidex in Canada occurred on July 25, 2007, when Carman, Manitoba hit 53.0. That number broke the previous record of 52.1 set during 1953 in Windsor, Ontario (The residents of Windsor would not have known it at the time, since the humidex had yet to be invented).
When the temperature is 30 °C (86 °F) and the dew point is 15 °C (59 °F), the humidex is 34. Note how humidex is a dimensionless number, but it indicates an approximate temperature in °C. If the temperature remains and the dew point rises to , the humidex rises to 42. The humidex tends to be higher than the U.S. heat index at equal temperature and relative humidity.
The humidex formula is as follows:
Complete:
Heat index
The "heat index" (HI, also "humiture") is a measurement which combines air temperature and relative humidity as being the human-perceived equivalent temperature — how hot it feels. The result is also known as the "felt air temperature" or "apparent temperature". For example, when the temperature is with very high humidity, the heat index can be about .
The human body normally cools itself by perspiration, or sweating, which evaporates and carries heat away from the body. However, when the relative humidity is high, then the evaporation rate is reduced, so heat is removed from the body at a lower rate, causing it to retain more heat than it would in dry air. Measurements have been taken based on subjective descriptions of how hot subjects feel for a given temperature and humidity, allowing an index to be made which relates one temperature and humidity combination, to another, at a higher temperature in drier air.
The heat index was developed in 1978 by George Winterling as the "humiture" and was adopted by the National Weather Service a year later. It is derived from work carried out by Robert G. Steadman. Like the wind chill index, the heat index contains assumptions about the human body mass and height, clothing, amount of physical activity, thickness of blood, sunlight and ultraviolet radiation exposure, and the wind speed. Large deviations from the typical values will result in heat-index values which do not accurately reflect the perceived temperature.
In Canada, the similar humidex is used in place of the heat index. The humidex differs from the heat index in using the dew point rather than the relative humidity.
The heat index is defined so as to equal the actual air temperature when the partial pressure of water vapor is equal to a baseline value of 1.6 kPa. At standard atmospheric pressure (101.325 kPa), this baseline corresponds to a dew point of 14 °C (57 °F) and a mixing ratio of 0.01 (10 g of water vapor per kilogram of dry air). This corresponds to an air temperature of 25°C and relative humidity of 50% in the sea-level psychrometric chart.
At high temperatures, the level of "relative" humidity needed to make the heat index higher than the actual temperature is lower than at cooler temperatures. For example, at approximately 27 °C (80 °F), the heat index will agree with the actual temperature if the relative humidity is 45%, but at about 43°C (110°F), any relative-humidity reading above 17% will make the Heat Index higher than 43°C (110 °F).
The heat index is calculated only if the actual temperature is above 27 °C (80 °F), dew point temperatures greater than 12 °C (54 °F), and relative humidities higher than 40%. The heat index and humidex figures are based on temperature measurements taken in the shade and not the sun, so extra care must be taken while in the sun.
Sometimes the heat index and the wind chill are denoted collectively by the single terms "apparent temperature" or "relative outdoor temperature".
Blue Velvet (movie)
Blue Velvet is a 1986 American mystery movie by David Lynch. It is set in North Carolina. The cast include Dennis Hopper, Laura Dern and Kyle MacLachlan. The title is from the 1963 Bobby Vinton song of the same name. This movie was originally detested by certain movie critics, although it is now widely acclaimed. It was controversial at the time of its 1986 release, and has since become a cult favorite. Lynch got his second Academy Award nomination for Best Director for the movie.
Charlotte Hounds
The Charlotte Hounds are a men's professional field lacrosse team that is based in Charlotte, North Carolina. The Hounds joined Major League Lacrosse (MLL) in 2012. They play their home games at American Legion Memorial Stadium.
Manhunter (movie)
Manhunter is an American crime thriller movie. It is the first film with the character Hannibal Lecter, a psychotic killer. It is based on a book by Thomas Harris, called "Red Dragon". The movie was written and directed by Michael Mann. It stars William Petersen, Brian Cox, Dennis Farina and Tom Noonan. It tells the story of a serial killer and the detectives who are trying to find him.
"Manhunter" shows the science that police use to find criminals. This movie was not the only movie made from a book by Thomas Harris. Earlier, "Black Sunday" had been made, but not with the character of Lector. Later, "The Silence of the Lambs", "Hannibal", "Red Dragon" and "Hannibal Rising" were also made from his books.
"Manhunter" did not get very good reviews when it came out. It did not make a lot of money in cinemas. It took $15 million to make "Manhunter" but the movie only made $8.6 million in the United States. Today the movie gets better reviews and is seen by more people. It is thought of as a 'cult movie'.
Will Graham (William Petersen) is an agent who worked for the Federal Bureau of Investigation. He retired after he caught a killer named Hannibal Lecter (Brian Cox). Graham is asked by Jack Crawford (Dennis Farina) to help with a new police case. Crawford is trying to find a killer named "The Tooth Fairy". Graham goes to the house of the killer's victims. He finds The Tooth Fairy's fingerprints there.