Class interval should always be a whole number and yet in this case we have a decimal number. The solution to this problem is to round off to the nearest whole number. In this example, 2.8 gets rounded up to 3. So now our class width will be 3; meaning that we group the above data into groups of 3 as in the table below.
Skeletons come in a number of forms, each suited for a particular set of lifestyles and environments. Skeletons can be rigid, semirigid, or soft. They can also be external or internal. Vertebrates have internal skeletons, called bony skeletons, which consist mainly of calcified bone tissue. Most invertebrates, such as insects, spiders, and crustaceans, have outer skeletons called exoskeletons.
Animals can have internal or external skeletons-while some do not have a skeleton at all. Insects have an external skeleton made of chitin. Sharks have an internal skeleton made of cartilage, and humans have an internal skeleton made of cartilage and bone. Hinge joints and ball and socket joints are synovial joints.The biceps and triceps muscles act as an antagonistic pair to move the arm at the elbow.n endoskeleton or internal skeleton is on the inside of the body. Animals such as fish, birds and mammals have endoskeletons. Your own skeleton is an internal one. The skull is part of the skeleton. Internal skeletons have advantages over external skeletons.