How to Find the Mean Absolute Deviation ( MAD )

Learn how to calculate the mean absolute deviation ( MAD ) of a data set.

The MAD is the average distance of all of the elements in a data set from the mean of the same data set. You can think of it as how far each piece of information is from the average.

Find the MAD of the number of sunny days a month in Sunnyvale.

Step 1. Find the mean
Add up all of the elements and divide this by the number of elements in the data set.
25,15,20,17,22,28,27= 154
154/7 = 22

Sunnyville has a mean of 22

Step 2. Calculate how far each element is away from the mean and use the absolute value because,  distance is always positive.

25-22 = | 3 |      3
15-22 = | -7 |     7
20-22 = | -2 |     2
17-22  |-5 |         5
22- 22 = 0          0
28-22 = | 6 |       6
27-22 = | 5 |       5
                         28
Step 3. Divide the total from step 2 by the number of elements in the data set.
28/7 = 4

So the MAD is 4

The MAD indicates how spread out your data set is.
A large MAD indicates a data set more spread out relative to the mean.
A small MAD indicates a data set less spread out relative to the mean.

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Simple Machines 10 Facts

Work is the amount of energy necessary to move an object. The further you move it, the more work is required. Simple machines allow you to do the same work with less effort. Simple machines are all around you. These bikes incorporate three simple machines.

There are 6 simple machines,

Lever,  Inclined plane, Pulley, Wedge, Screw, Wheel and axle

If you start looking around you will find these simple machines in your everyday life.

1. A bicycle uses several simple machines including levers, wheel and axel, screws, and pulleys.

2, A skateboard ramp, and steps are examples of inclined planes.

3. The main function of a wedge is to change the direction of the input force. For example, if we drive a nail into a board  the nail acts like a wedge and  will redirect this force outward, causing the nail to go into the wood and sometimes split the wood

4. Scissors are a combination of a 1st class lever and a wedge. 

5. An ax is an example of a wedge.

6. A screw is essentially a long inclined plane wrapped around a shaft.

7. A wheelbarrow is a 2nd class lever and a wheel and axel working together.

8. Everyday pliers use a 1st class lever to increase your gripping power.

9. An inclined plane is used in ramps in order to help move heavy objects upward.

10. A hockey stick is a 3rd class lever that allows you to strike the puck with great force.

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Beginners Guide: Major Muscles of the Human Body

Beginners guide to the muscles of the human body.

The muscles in your bodywork with your bones to help you move in a huge variety of ways.
There are over 600 muscles. 

 Pectoralis major: is a thick, fan-shaped muscle, situated at the chest of the human body.
If you go to the gym and bench press you are using this muscle.

The Bicep is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. The function of the bicep is to flexes and twists the forearm. If you are working out and completing curls, the bicep is being flexed.

 The abdominal muscles support the trunk, allow movement and hold organs in place.

The sartorius muscle is the longest muscle in the human body. It is a long, thin, muscle that runs down the length of the thigh. This muscle helps you cross your legs.

The abductor muscle group is located on the lateral side of the thigh and moves the thigh away from the body’s midline. 

The trapezius muscle resembles a trapezoid or diamond-shaped quadrilateral. The trapezoid would run from your head to your shoulder, to midway down your back.
It helps support the weight of the arm and move the shoulder.

The deltoid forms the rounded contour of the human shoulder. It is a major mover of the arm. When you lift your arm from your waist to overhead you use your deltoid.

The latissimus dorsi is the largest muscle in the upper body. It is responsible for extension, adduction, and internal rotation of the shoulder. This muscle helps you do pull-ups at the gym.

The serratus anterior is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest. It acts to pull the scapula forward around the thorax.

 The external oblique functions to pull the chest downwards and compress the abdominal cavity, It also performs same side-bending and opposite side rotation.

The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. For example, when you use a  hammer to drive a nail you flex this muscle.

Finger extensions include nine extensor muscles found in the posterior side of the forearm and extend the hand and fingers.

Finger flexors help you close your hand.

Quadriceps is a large muscle group that includes the four prevailing muscles on the front of the thigh. These muscles are the great extensor muscle of the knee. When you ride a bike the quadriceps are used to push the pedals.

A  hamstring is one of the three posterior thigh muscles in between the hip and the knee.  The hamstrings cross and act upon two joints – the hip and the knee. When you run the hamstrings pull the heel to your buttocks.

The gastrocnemius forms half of the calf muscle. Its function is flexing the foot at the ankle joint and flexing the leg at the knee joint.

Tibialis anterior is responsible for flexing the foot backward and inverting the foot.

The soleus is a powerful muscle in the back part of the calf. It runs from just below the knee to the heel, and is involved in standing and walking.

The infraspinatus muscle is a thick triangular muscle. It is one of the four muscles of the rotator cuff, it’s the main function is to rotate the humerus and stabilize the shoulder joint.

The teres major helps rotate the humerus and assists the latissimus dorsi in drawing the previously raised humerus downward and backward.

The triceps are large muscles on the back of the upper arm. Triceps are responsible for straightening the arm.

The gluteus medius is a muscle that helps with hip movement.
When you walk and run it aids in stabilizing your pelvis, in particular when you perform activities where you balance on a single leg.

The gluteus maximus is the main extensor muscle of the hip. You use the gluteus maximus when you stand up from a chair, sprint, run, and go up steps.

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10 Fun Mountain Facts

The Earth has a huge variety of different terrain. Some of the most beautiful and majestic locations are mountains. Mountains can form through folding, volcanism, and faulting. Let's learn 10 fun facts about the Mountains.

1. Volcanic mountains are created when melted rock erupts onto the earth’s surface. Many volcanic mountains occur at convergent boundaries. Most of the active volcanoes are concentrated around the edge of the pacific ocean. This area is known as the ring of fire.

2. Fault block mountains form when tension causes the lithosphere to break into normal faults.
At normal faults, the lithosphere drops down. The pieces left standing form fault-block mountains.
The Teton mountains are examples and the Sierra Nevadas.

3. There are at least 109 mountains on Earth with elevations greater than 23,622 ft above sea level. The vast majority of these mountains are located on the edge of the Indian and Eurasian continental plates.

4. Mount Everest is the highest mountain on Earth at 29,021 feet and is celebrated for this, but K2 is almost as tall at 28,251 feet tall.

5.  The Barberton Greenstone Belt in South Africa are considered by most scientists to be the oldest mountains on Earth.

6. Many people love to ski down mountains and the largest ski resort in the world is Les 3 Vallees in
France.

7. Mount Saint Helens is a volcanic mountain and is most famous for its huge eruption on May 18, 1980, the deadliest and destructive volcanic event in U.S. history.

8. Most geologists would define a mountain as a landform that rises at least 1,000 feet above its surrounding area.

9. Belarus is the largest country without mountains.

10. Kyrgyzstan and Tajikistan could be considered the two most mountainous countries with over 90% of the country considered to be a mountain.

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10 Facts about the Layers of the Earth

Earth can be divided into three layers based on chemical composition: the crust, the mantle,

and the core, and based on physical properties, such as whether the layer is solid or liquid.

The five physical layers are the lithosphere, asthenosphere, mesosphere, outer core, and inner core.

1. Although the core is very hot, it is solid due to the tremendous pressure placed upon it.

2. The asthenosphere is made of solid rock that moves very slowly. It is described as viscoelastic which means it can flow and can also be elastic.

3. The lithosphere is the outermost layer of the Earth and is around 100 km thick. The lithosphere is divided into pieces called tectonic plates.

4. Alfred Wegener was the first Scientist to suggest these huge tectonic plates actually move around the Earth.

5. The inner core is the hottest part of our planet, with temperatures between 9,000 and 13,000 degrees Fahrenheit. (5,000 and 7,000 degrees Celsius)

6. Oceanic crust is denser than continental crust due to the increased mass of the ocean which is found above it.

7. The mantle is located between the crust and the core and is a region of hot, slow-flowing solid rock.

8. The outer core is composed mostly of liquid iron and nickel.

9. The crust is very thin compared to the mantle. The crust on average is 30 kilometers thick compared to the mantle which is 3000 kilometers thick.

10. Tectonic plates are made up of plates crust and the outer mantle. These plates move sometimes strike each other causing earthquakes, mountains, oceanic trenches, and volcanoes.

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10 Facts about Levers

A lever is a simple machine, that is the basis of many tools in and around your house and work.
The way levers work is by a force is applied at a point, which moves a load at another point through a balance point called the fulcrum. It is the relative positions of these three points - the force, the load, and the fulcrum - that distinguishes the type or class of lever. There are three classes of lever 1st, 2nd, and 3rd class.

1. Archimedes had this insight about a lever, "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world."

2. A wheelbarrow is a class 2 levers that allow you to carry heavy loads.

3. Scissors are actually a wedge combined with a 1st class lever.

4. Pliers allow you to multiply your gripping power by using a 1st class lever.

5. A see-saw is a regular fixture at playgrounds and uses the power of a 1st class lever.

6. Hockey players use the leverage of a third-class lever in order to shoot the puck at great speeds.

7. A golf club is a 3rd class lever.

8. A 1st class lever has the fulcrum is in the middle and the force is on one side and the load is on the opposite end. 

9. A 2nd class lever has the load between the force and the fulcrum. 

10. A 3rd class lever has the fulcrum on one end, the force in the middle, and the load on the end.

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Types of Faults in Geology

The Earth is a dynamic and constantly changing place. the tectonic plates which sit on the asthenosphere shift and move. This movement creates stress, and rocks at the surface may break in response to this. When rock breaks, cracks are created which are called faults. On either side of the fault are blocks of rock called fault blocks. When these fault blocks move, earthquakes may occur.

There are three main types of faults. Strike-slip faults, normal faults,  and reverse faults

Lets first determine the difference between the hanging wall and the footwall. In all faults, except for vertical faults, the hanging wall is the block above the fault and the footwall is below.

Two simple ways to identify the foot and hanging wall is to place your finger on the fault surface and move it up. It will automatically be located in the hanging wall. The hanging wall will have an angle less than 90 degrees at the top and the footwall will have an angle greater than 90 degrees at the top.

In a strike-slip fault, the blocks move past each other horizontally. A strike-slip fault occurs due to shear stress which pushes the rock horizontally but in opposite directions.
Strike-slip faults are common along transform boundaries like the San Andreas fault.

During a normal fault, the hanging wall moves down relative to the footwall. These faults are called normal because this is what you would normally expect the faults to do. Normal faults are a result of tension that stretches or pulls the rock apart. Normal faults are common along divergent boundaries. The basin and range area is an example.

A reverse fault occurs when the hanging wall moves up the footwall. They are called reverse because this is the reverse of what you would expect as a result of gravity.
Reverse faults occur as a result of compression which is a stress that squeezes the rock together.

The San Gabriel mountains are caused by reverse faults.

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