A dollar invested in a house in 1968 was worth $1.29 in purchasing power in 1978, according to a newly published report.

The same dollar, if invested in a common stock, would have been worth 78 cents, according to a study made by the Mortgage Bankers Association of America. The dollar would have had 89 cents in purchasing value after 10 years if it had been in savings account but would have been worth only 53 cents if held in the owners' pocket.

According to MBA Executive Vice President Mark J. Riedy, the report demonstrates that the single-family house is "one of the few assets that has fully protected the purchasing power of the dollar in the past decade. Only an investment in a corporate bond would have increased the purchasing power -- to $1.20, still less than the housing appreciation," Riedy said.

In a comparison of the cost of renting, the report also illustrates that owning a $63,000 house (the average price in 1979) would put the individual ahead financially in comparison with renting after 14 months. This assumes an 8 percent yield on alternative investment by the renter and a 12 percent mortgage with a 10 percent down payment, plus closing costs, by the buyer.

The report is based on housing appreciation figured at an annual rate of 10 percent (less than in the Washington area during the past five years) and income tax advantages. However, in assuming that the owner would be $35,000 ahead of the renter after five years, the report does not consider that the owner would be selling and be taxed for accrued capital gains.

Riedy and MBA economist Thomas Harter discussed the report at a joint press conference yesterday.

In discussing the current housing and mortgage markets, both Riedy and Harter said the recent housing slump is leveling off and that demand for housing is expected to be strong this fall and next spring if mortgage rates are less than 12 percent. They conceded that most demand now is for the FHA-VA loans for which funds are adequate. Conventional mortgage rates are generally slightly higher but moving lower because of a lack of demand.

But Riedy warned that "the buyers' market is likely to continue for less than 90 days." He said he expects slightly lower mortgage rates this summer to bring buyers back into the market and result in a new demand for housing. This would result in another upward spiral in both prices and mortgage rates, the officials agreed.

Riedy said purchasers would have to buy this summer to get in at the bottom of the cycle.